It's a really difficult situation, and impossible to give advice without knowing a lot more. Personally, I'd let the DD know before the holiday, and have a serious discussion about whether you do on the holiday or not.
A few years back, we had a family holiday, and I knew DSis and her DH were splitting, but a lot of stuff had been arranged, rental, travel, three families, logistics, etc.
DSis was awful on the holiday, drinking too much, on the phone a lot to another man (shagging her BIL ffs!!), passive aggressive, more details were revealed during the holiday, it was a nightmare. She should never have gone.
I guess my point is that don't go away unless you have discussed it. It could turn out awfully bad for you all, including DD unless you realize what you are getting in to.