This is the guy that didn't buy his own daughter a present.. or even a card for her 6th birthday... yeah.. father of the year there.. better make him feel good.

Honestly, it's nice if an EX helps a small child get something for the other parent on those occasions.. but it is NOT required.. and if they have a not so great relationship.. I can see the ex not wanting to be involved.. in fact sometimes we have people here complaining the "ex" got their SO a present.. so That, in itself, is not an expectation I would have of the EX.

You are his wife.. you know he has a 6 year old that is not independently capable of doing things like this.. the nice thing would have been for you to facilitate a gift/card from her.. and your younger kids..   No, she isn't your child.. you are not obligated to do any more than you want.. but she is a small child that lives in your home.. at least part time.. so helping her be a better person.. to think of others on special days etc.. it's probably the right thing to do.

I mean.. I'm really stuck on the fact that when the girl turned 6, her dad didn't get her anything.. and that would have been something I would have felt bad for the little girl.. and my attitude would not have been "he didn't.. so I"M not going to either"  I personally would have bought a little tiny something.. not expensive.. but dang.. the little girl is 6.. maybe she is jealous of your youngers.. but being treated that way doesn't help her feel more part of the family does it?

I'll use me as an example. Both as a BM and also as a SM.

As a BM as long as my children were young, I helped them make a gift. A craft, a decorated picture frame, etc. As they got up to double numbrs (10 ish)  I offered them the chance to do chores to earn the moey to purchase a gift. This is easier now because of on-line shopping. After they had part time jobs they were given one reminder and then it was on them. 

As a SM, I offered to help w/ a craft. One year I helped him buy (at a garage sale)  a small candy dish that fit with her collection and he picked out a bag of candies to put in it. As her got to double numbers, his dad would ask him if he wanted to do something for mom and if so, gave him a $ amount (usually $10) to stick to and took him to buy it. Once he was a teen and working a part time job, it was a gentle reminder .

In my situation, BM/DH don't help SS with Mother's/Father's Day gifts. Part of it is long distance during those holidays and part of it is toxicity in the co-parenting relationship. DH used to help SS figure out small Mother's Day gifts for BM, but when it was met with toxicity, he stopped. Plus, BM had a new partner by then, so DH felt it would be more appropriate if the new partner took that on instead of DH. 

For DH's birthday and Father's Day, we usually have SS, so I tend to take SS shopping for a card or gift. BM's partner, I'm sure, does the same thing for Mother's Day and BM's birthday. Each household does their own thing for Christmas, with the SParents helping SS find a gift for the respective parent of that household. 

When the SDs were young, I did help, but once they were around 14 I left it up to them to skip or figure it out.

This year, shocker, YSD DID stay the night last night. However she didn't give DH anything, not even a card, and helped with nothing else. I think she did some of her own dishes, but not all. Her and DH have piles in the kitchen which will likely be there tomorrow still because they have to go in early fir graduation and DH won't be back till later.

While I'll take care of Dhs special dinner stuff I refuse to do YSDs extra food prep things, random dishes throughout the day and DHs dishware from the entire day. The damn dishwasher is right there.

In this situation I would make the card from you.  Don't say it is from the kids, any of them.

Try "Thank you for being such a great dad to (List the kid's names)"

Once your kids are old enough to do it for themselves, then let them do it. If the Skid does not participate, at that point it is on the Skid.

My SS is an only in our family. I give my bride M-Day cards every year. One always thanks her for making me a dad.  I do not give them to her from SS.