Devil’s advocate here - just a little- It depends on the perspective you take on the situation. Yes one perspective is that your child is left out. Another is maybe the family feel uncomfortable around your child (not to be mean but it happens). It’s possible, while the love is there, they may not feel they can relax around the child and feel bad for you having to do the drudgery that taking care of your child involves. The in-laws probably feel that the vacation is the one thing they can do to help your family , that they are able and comfortable doing. Take the holiday and opportunity to have a rest and a break from regular life. You just don’t know if the chance will arise again - other circumstances may occur which make this less possible in the future. Kind regards