Reading this post has made me grateful I am spending Christmas alone with DH this year! I am an un-confrontational person too and hate drama (part of the reason we are staying alone!)
First of all be glad at least DH has insight into how difficult his DD is and is trying to deal with it.
I think preparation for the visit is the starting point.

I used to find myself engaging more with the sgrandkids but they don't visit anymore. I think you need to accept that if there is discord in their presence it is not your place to take them out of the way, though I understand why you would do this. Maybe they are used to being part of that family circus.

These are the things I would do if it were to happen to me.

1 Not be around when they arrive if possible- if you know when they are coming take yourself for a walk or just sit upstairs
reading a book
2 Be polite but distant-
3 Be in charge of the food and drink- this gives you something practical to do which means you only exchange niceties and spend most of the time in the kitchen
4 Prepare a get out in advance- this could be a call from a friend or relative, remembering that you have something to do
elsewhere etc, devote time to a hobby, go for a run etc
5 Drink, and keep drinking until you do't care anymore, or get a bug or migraine which means you have to spend time in your bed

Apart from this I would suggest you keep calm- if there is a drama just clap inside your head as if you were watching it on stage and say to yourself that it will be over soon...

'outsmart her stupid games and let my husband have what ever little time he will have with his grandchildren a non-stressful visit". You've answered you own question right here. Be polite say hi, give hugs(if you want), dote on the sgkids a little, be general and brief with her DH as you would anyone else you first meet and find something else in the house to do.

As far as going out with them, I would get a feel of how they behave and decide if I will go. Even though your DH asked you to join, you don't have to be in an uncomfortable situation to appease him, I'm sure he would understand.

I don't think you need to plan for anything, because your DH has your back. That makes all the difference in the world. When our DHs don't have our backs and the SDs are so good at turning on the charm and convincing daddy how sweet and innocent they are, our DHs wonder why on earth we would have a problem with their little cherubs.

Just ignore her, other than saying a polite hello. Focus on people who like you. Let her play her games to an unreceptive audience and fall flat on her face. You wouldn't waste time on other unfriendly unwelcoming people. SD doesn't get special privileges because she is your DH's daughter.

Here's my tried and true list of tips for being in the same universe with my SD - and I am serious about just nearly every point:

Definitely keep busy. Take a dish that needs constant stirring or why not carve your ice sculpture right there? Clear the table, do the dishes, wash their car take on the challenge of building an addition for your hostess. Do whatever you have to do - keeping busy is crucial!!!

As soon as you get there, eye up the seating arrangements in all rooms and figure out the one closest to an exit and lay claim with your giant purse. This is so you can slip out to the bathroom, or to sharpen your carving blades...for the sculpture, of course. If you choose your seating wisely, you can even slip out just to slip out with no pretense necessary. It's all about being closest to the next room when you feel your blood starting to bubble.

Engage the nonpolitical people early on, especially kids, who won't think it's strange if you plop down and start coloring with them or building a cone of silence around yourself with their Legos. Identify the narcissists and crazy aunts who will talk your ear off so you can willingly be stuck as an audience of one all night to avoid SD altogether. If you check in with these folks early on, you can always jump back into conversations with them when you need an out.

No matter how much you need it, deserve it and will indulge the second you are out of there, don't drink! You must be on your guard so you don't slip into a trap! Ditto on prescriptions tranquilizers (I learned this one the hard way).

If you have a dog and it's a dog-friendly event, take your dog! (This is my secret weapon, but I'll tell you if you promise not to tell anyone else!) Dogs need to go out for walks and bathroom breaks, they need to be held and fed, they need sweaters put on and sweaters taken off, they are fantastic, nonpolitical talking points (especially if yours is hairless like mine) and people are always eager to talk to you about their own dog when you have your dog there - often they'll talk incessantly about their dog, so there ya go over engaging again so you can avoid other people in the room. Eagerly look at their videos and photos when they whip out their phones. If you're anything like me, you can practically spend your entire night alone with your dog in a room full of people you want to avoid. And above all that, petting your best friend will KEEP YOU CALM when things get tense!

If you are in a position with your husband to do this, have a safe word to signal a speedy emergency exit or slower-mo wrapping up of the evening. He will probably ignore the safe word even if you take this route to agree upon one because men are so clueless, but you can say the word then add the double-eyeball hike at him when no one is looking to remind him you've been saying "gobsmacked spray painted pyramid" for the last two hours. (I suggest a safe word that is in context. Learned this one the hard way too.)

Discuss and agree ahead of time what time you should leave the event so you don't slip into "stayed five minutes too long" territory. It only take five minutes to end up with a homicide charge or at least a bad-form move everyone will remember for years to come. I actually find my husband using this tactic with me and my family loves him. This also keeps you from being the last ones remaining with only SD in a small, awkward situation. You want to arrive after a few others get there and you want to be among the first to exit.

Discuss and agree what subjects should NOT be discussed in front of SD or with SD. Figure out what topics you don't want to discuss with SD if you talk alone with her and if they come up, pull down your Lego cone of silence or leave the room. Tell husband what the topics are and let him know you'll be exiting the situation if it gets uncomfortable or downright ugly and he can find you walking the dog...or perhaps at home, depending on how long it takes him to notice you left with the dog.

See, I had just more than a year to hyper-plan with statistical precision every possible negative scenario that could occur at my SD's wedding (also attended by my husband's ex, who terrifies me). I cooked up this list then and I think it's pretty comprehensive, barring SD swallowing a bone and wondering if I'm legally obliged to Heimlich it out. (I'm not.) I believe it worked. The entire event sucked and I had PTSD when I left, but I was ready for anything and felt more confident being over prepared.

If you're determined to go, this is about all you can do - you'll be in range and she'll be armed and loaded. Be sure to smile at SD (others will be watching), and constantly remind yourself that it will be over soon and if you can escape without an incident, your charm, wit and warmth will be noticed by others.

I admire that you're determined to go. My "ways to distract at wedding I'd rather die than attend" list lies in waste now that I've 100% disengaged from my SD. But I dig it out every time I have to see my own family. And remember...be careful with those ice carving knives - cold, wet hands make them slip so easily and they can land in ANYONE's skull.
Good luck! YOU CAN DO THIS!

Oh, this is deja vu for my Thanksgiving with SD57 and SGD33.

Your situation has not reached the point of disengagement as mine, yet. Hopefully your DH continues to have your back. Mine did not.

God Luck
You sound like a giving person.

((hugs))

Skids like this literally shoot themselves in the foot when they try to punish daddy for daring to remarry and finding happiness. I'm sure you and DH would spoil those gkids rotten given the chance. It's terrible that she is depriving her children from two grandparents who could be an amazing support and loving influence in their lives.

Your plan of baking cookies w/gskids and focusing on them is great. Hopefully SD will visit w/dad and behave herself.