I've recently been to a family dinner at a restaurant. It was to celebrate my 8 year old cousin's birthday and there were only 9 people in total. I despise all family events and my family knows that. I always get bored, since I don't have anyone to talk to (I'm 16 and the cousin in question is the oldest other child, the rest are adults that talk about the colour of rugs they prefer...) and I'm frowned upon when I use my phone. 

I was only informed about the dinner the day before (as my cousin's actual birthday is in two weeks, I wasn't expecting it).  The restaurant we went to was moderately priced, but the waiting times for the dishes were pretty long. In the end I managed to wait for the main course, and I never get dessert anyways. It was a painful 2,5 hours and I've been desperatelly trying to entertain myself during most of it (maybe half an hour was actuall eating). During the whole dinner, I've been moaning to my mom about how I dislike being there and whether I could leave. She always told me to just grin and bear it. When my family started to order desserts, I finally snapped and told her I'm going home. I thanked and said my good byes and went to the bus stop.

I'm not worried about dissappointing my cousin since he wasn't very happy about being there either, he'd rather go to some fun place and not a boring restaurant. My mom is pretty understanding and just shrugged about the whole thing but my aunt (cousin's in question's mom) and grandma (aunts and my moms mom) are easy to be annoyed and pout. They're really the only 2 people that actually enjoyed the dinner.

AITA for not waiting another 1-1,5 hours of complete boredom, which would satisfy my maternal grandmother and aunt?