When we were at my in-laws over Christmas, one day when it was just DH, MIL and myself we were chatting and my husband, without discussing it with me, just throws out there "does she want to come along on our next trip and babysit".
Seriously

, the man is so infuriating at times.
A) we hadn't actually decided if we were going to ask her along or not
B) she certainly will not be invited so we can have a babysitter
and
C) why would she ever want to come now, the offer was hardly heartfelt.
I was really cross with him I have to say, it was definitely not the time for it and definitely not the way I wanted her to be asked, our intentions are out of kindness and the way he said it sounds like we only want her to come to mind our children. Grrrrrr
Anyway, she laughed and said "sure, if you pay" and my DH did a joke cough cough at that. This was the end of the conversation.
Then a few days later a family member was visiting and we were talking about travel because this family member has travelled a bit and my MIL says "oh yes and the kids have offered to have me along on their next trip" with a smile on her face.
The family member looked at me with eyebrows raised for confirmation and I just said "of course, MIL would always be welcome to come with us"
So I guess the offer is out there kind of now, although obviously the "terms and conditions"

are all confused and would need some discussion at some point.
On the surface it looks like she would be keen but it would come down to money for her in the end I think. DH and I have discussed that we will definitely absorb all of the accommodation costs now, work out some sort of daily meal allowance so she doesn't have to think about that throughout the trip and she can just pay for her flights and activities.
Because we cannot really discuss this with her any time soon on any real level, I am going to have to look at accommodation for WDW and NYC that would work for everyone and book that. The remainder of the trip's accom I can book closer but I would like to get WDW and NYC locked in soon. I think we will go with Doubletree Suites in Times Square because even if she doesn't come along, it will be nice to have a little more space over Christmas time. As for WDW, we think we will have to get 2 rooms at POP which is a shame, I would have loved to do a split stay with one of the Deluxe resorts but for sheer cost, 2 rooms at POP is more affordable.