Feeling very left out and sad

Maybe the MIL bought the tickets and treated everyone? It might not be that you were consciously left out.

I do understand, as although I'm not a granny yet, I know that if I am blessed with grandchildren I will be 'the other granny' unless something radical happens, as both of my children live in different towns miles from me, and their ILs live near them. I would love to be able to help with childcare, but it won't happen as we are too far away. I could maybe go and stay in the holidays, but even that's not the same as the day to day contact that my sister has with her grandchildren, who all live in the same town.

Try not to be hurt? Can you organise something to give your DILs some time off? I don't know the ages or numbers of the grandchildren, so it might be too much, but could you have them to you for a sleepover - a film night with pizza or something similar that's fun without being too much like hard work? You could make it a pyjama party with streamers and hats, if age appropriate. My children loved that kind of thing.

I bet you feel a bit sad, I would too. Can you mention it to your family and tell them how you feel.