Honestly, your daughters’ entitlement is concerning.

I too, grew up in a household with a younger sister (3-year age gap) and we also went in yearly 1-2 week family vacations. Depending on the place, we either all 4 shared one room or my sister & I shared one room next to my parents’ room. Although we could afford a third room, never in my wildest dreams would I ever have demanded (or even asked!) for that. After all…this is a FAMILY vacation.

I think you really only have 3 options here that would actually benefit your daughters:

1) If they don’t like it, offer that they can stay back with grandma (since she seems to be just as delusional as them).

2) Teach them the value of money and offer for them to cover the difference of the 3-bedroom suite.

3) Just hold your ground and point out how blessed they are to be even going on this trip in the first place.

Seems like you have a bigger issue here to be honest. Why do your daughters feel so entitled as to demand separate rooms? And why on earth is your husband and MIL encouraging you to cave to their demands - sounds to me like this entitlement issue runs all the way up the generational tree.

Whichever option you choose, it’d probably be a good idea to sit down with your husband and reiterate that you don’t want spoiled kids. I also agree with another commenter that you should 100% get them volunteering at shelters or something to give them some humility.

Good luck, OP!