We are always left out of family plans.

Bit of context I have an older autistic son and a younger son with possible ADHD. He doesn’t sit still and gets very hyperactive especially at this time of year and when he sees his cousins which is very rare. Nan (husbands mum) know how tough we have it particularly at this time of year when everything is different and overwhelming for our son. We were invited to come and see the cousins around the nans house (huge lovely house). We go there after a day out and can see a lot of effort has gone in to decorate the house and the dinner table has been set up with two kids plates and adult plates, all laid out lovely. We were going around just for a coffee because we didn’t get invited for tea. Anyway my son gets hungry they offer him a bit of curry, he’s sat at the island, not on the lovely laid out table. Anyway the cousins and the sister (there mum) are staying over so start getting the kids ready for bath time. We have never stayed or been invited to stay. They are obviously going to all sit and have this nice meal when we are gone. Then on leaving I learn the sister and the cousins are staying over Xmas (the nan said they was staying until Xmas eve). We was not invited over with our children on Xmas day and it feels like we are excluded and our children are being excluded by the very people that are supposed to include them. Am I being an asshole for being really pissed about this? I just feel like we are an after thought, every thing is planned without even thinking about whether we would like to be invited. We have told them in the past we feel excluded but I just feel like we aren’t good enough to be included in there plans