MoaningTurtle, please don't let this eat you up! I understand your are hurt but if your DIL does'nt want to go on holiday with you why would you want to do that ? It may be that she simply wants a holiday with her DH and their children - just them and perfectly understandable. She may prefer a holiday with her own parents and hard as that is a daughter may well lean towards her own parents rather than her parents in law - again very understandable! It is a complex situation, I can only say that when we were bringing up a young family I loved going away with just my DH and our children. Clearly you are upset but try and ride this out for the sake of everyone, I am sure your son would rather go away with you but he has his wife to consider and trust me regardless of his feelings he will side with her - it's inevitable so I am afraid you are going to have to accept this or damage the relationship you have with your son . He may well be as upset as you but is in a very difficult situation so if you cause a scene about this you are only adding to his anxiety and I am sure that is the last thing you want to do. Accept their decision, smile and book yourself a lovely break at the same time your son , DIL and GC are away and very importantly enjoy it !
Family situations like this can rapidly damage family relationships, please do not allow that to happen.