Accept that she and the twins aren't coming and go on with the show. Truly, there is no reason her lack of attendance is cause for frustration or disappointment, unless YOU want it to be. They are not necessary to have your holiday celebration, and if she's as weird and problematic as you say, it's probably best that she's not there.
As for the twins, let me tell you, they can be a doozey to handle. You have no way of knowing if there is a problem with the kids. Perhaps they don't do well in large crowds with lots of stimuli and excitement. I had a child like this and my in-laws were totally unsympathetic and when I did relent and bring my highly excitable toddler to celebrations they were the first to get totally bent out of joint and attack me for having bad parenting skills if he had a melt down or started acting out inappropriately. That kid only did well at small intimate gatherings with no loud noise, smells, lights and craziness. Too many faces and voices sent this kid over the edge. It wasn't until he was older I discovered he had a sensory disorder and I was rightful to avoid bringing him to stuff like that. Nonetheless, my in-laws refused to accept the kid did not do well at stuff like that nor did they even care that it could take him days to recover (emotionally speaking). Instead they chose to take it personally and make it an occasion for blame and to accuse me of "ruining" their life, plans and family celebrations.
I use the word choose because I tried to tell them my reasons for my actions but they wanted to believe what they wanted to believe and suffer at their own hands. It's all a state of mind and perception, I say. If you want to let your daughter-in-law's choice to keep the twins home to be cause for a miserable holiday, that's your choosing...not hers. She's only being a parent and parenting in the way she sees fit. You don't have a right to foist your way of doing things on her, when it comes to raising her children. She's the mom and you need to respect that. If she were really trying to ruin your holiday or be difficult, she wouldn't bother sending any of the children to celebrate with you or worse, would bring the whole clan even if it means actually and truly "ruining" your event because someone isn't up for the activity.
Do not be negative. Be more understanding and patient. It isn't worth ruining and breaking up your family over mere perceptions and assumptions. You can never really know a persons motives, and 90 percent of the time, people aren't purposefully working to spite others. Each person has their own challenges and burdens and is doing the best they can to function the best they can while helping and accommodating others. To me, it sounds like at this stage of your dil's life, she feels it important to keep the twins home. I say respect that. It isn't worth wrecking the family over it.
I speak from knowledge...my mil...the one who didn't get it about our son pissed my husband off to the point where HE doesn't want to come home anymore and hasn't. I never saw this coming...I expected years of having to tolerate my extremely sensitive mil who thought I was purposely trying to ruin her life...and instead she wound up ruining her relationship with her own son...by her own choice.
I don't mean to preach, but I share this as food for thought.