C.A.
Hi J. O,
I do not know the whole situation however it sounds very familiar to me. I have a mother in law that is not very welcoming herself!!!! I am 34 years old married and have two little ones at home, therefore what I am eluding to is that time and grandchildren still have not helped my situation:( My husband has finally went to bat for me and sticks up for me if she decides to be fistey..... I think the best advice without knowing the situation would be to have the kids stick together; if her boyfriend really wants her to go then have him insist that she comes along and if his mom disagrees then he can do something else with your daughter and give mom a little tough love!! Hopefully they can just explain how being together is important to them and that they would really love to take the trip together with the family:)
I hope this can help somewhat.......
C. A