I know it would be awkward but it might be a nice getaway for you. If you fly there, no need to sit in a hotel room by yourself all day. Rent a car and do some sightseeing. If the thought of this doesn't appeal to you, stay home and do something nice for yourself. Weird that the other SD and DH text/call each other so often. Sounds like intense codependency going on there. Good luck. 

Unless there thing to do.  Then you  must stay for a few days for ... Hotel spa day ...Great restaurant....places to go...thing to do...  as turning it into a vacation.  

you have plenty of time to start scoping out the events, museums, parks, etc. in that area. look into what it offers and then make your list of to do things to do while he's at the wedding. 

I refused to attend DHs oldest son's wedding, even though I was invited. Not breaking my boundaries or my disengagement rule. Add in it was during CoVid during a surge in their state; bad enough, DH did not attend due to his own health concerns. But regardless, I would not have attended. 

We have a new issue to deal with and that is age. DH is older than me by 7 years and I'm not sure how safe it will be in the near future for him to travel alone. So...that means, I'll have to fly with him. NOt a problem. I have a art/craft form that opens doors for me to find "entertainment" when in the area. My "group of people" are the type, if I say, I'm coming to X city for 5 days and want to connect, there will be mulitple invites from people and shops. So, that's my plan....to fly with him to the destination but have my own schedule and agenda. 

Either way, you have two choices. Stay home and enjoy the down time (which I also love) or plan yourself a little trip, filled with fun things, food, wine and massages. 

It's not your fault that an adult SD chose not to develop a relationship with you and never accepted you.  It is, however, to your credit that you come from/have a family who is accepting of your DH.  Your DH lucked out; you got the short end of the stick. Does HE feel guity about that?  Probably not much.  His darling daughter probably can''t do any wrong, even if it is rejecting you.

IMO you should not go. Even if it is a small ceremony weddings often bring out the worst in people.  However, your DH will be expected to go to this and that activity, which means leaving you on your own.  On the surface, this doesn't seem like a bad option.  But I'd encourge you to think it through. 

The last time I visited SD's area I did spend several days visiting with my own friends there. I kept my exposure to her and her clan to a minimum.  BUT ... I was still slightly annoyed because I was essentially in exile, albeit due to my own self-inflicted choice. Yet it was clear that no one wanted me there or I imagine they would have tried harder to include me. But they didn't.

Who needs that? 

I'd much rather spend my time/money going somewhere I chose and doing things based on my timeline.  Because even if you go and plan to do what you want, you will find yourself still trying to "schedule" things with your DH after he prioritizes SDs/wedding events.  In my case, it still rankled even though I said nothing.

I will never try and go that route again, that's for sure. 

Be radiant and beam your happiness on your DH's arm.  Go dressed and made up to the 9s.  Go get a new hair style, a professionally selected make up palette,  wearing a rockingly HOT dress and a smokin hot lengerie ensemble underneath, and some flaming hot designer shoes all from your favorite boutiques.  Go all out with class. Whisper sweet little promising inuendos in your DH's ear periodically throughout the event so he will be radiant as well.

Have a number of scripted one liner responses to select from as needed. If you have them pre-reviewed you can modify them mentally and drop them in conversation as needed.

'Oh, how beautiful. SD, you would have loved your dad's and my wedding.  I so sorry you chose not to attend.'

'Bless your sweet little heart.' (The SouthernBell version of ... 'F-off and die')

'It is soooo nice to see you again.  Going forward, please do not make it so long before you spend time with your dad. We are having such a good time celebrating with you.'

Perfect the semi smirking smile and let your eyes twinkce with mischief.  Keep them all guessing and rocked back on their heals.

When you radiantly enter, the toxic will scurry for the dark shadows like throwing on a light in a dark roach filled room. Roaches nearly always scurry. As they should.

Have fun and blow them all away with the demonstration of your happy life and marriage.