I'm 23, for context. Every year our family go out for a Christmas meal with a family friend's family. I'm not particularly close with the family friend or their family, but my parents say I'm being self-centred and miserable if I don't go. The family friend has been kind to me at times, but also quite judgemental of me (my parents tells me what they say).
I've recently had to start on a restrictive diet due to a health diagnosis (don't want to go into detail), and nothing at the restaurant we are going to is suitable for me to eat apart from a bowl of chips (which I'm already skeptical of as they have seasoning I don't trust). The family friend doesn't seem to believe me about the diagnosis and is dismissive about it, despite knowing the symptoms I experience and the trips to the doctors/hospital I've had.
AIBU to not want to go for the meal this year? My Dad is annoyed with me that I don't want to go, as he says I could just sit there with a drink and eat when I get home. We could have easily booked another restaurant that was suitable for everyone (literally every other restaurant I've been to has had at least one suitable meal option for me). When we've been with meals with this family before we've had to go to certain restaurants as one of them is quite fussy, so it's not like we're not flexible and accommodating to their needs.