Realistically, the more upmarket a place, the more likely it is that anyone "larger" will get one or two looks from very thin women who are never going to get to go anywhere nice unless a man pays for it, and who have absorbed the message from the cradle that you "get a man" by starving yourself, and who seem to resent any larger woman who's having fun and not even hungry. You've evaded your proper share of feminine suffering, you see. Anyone who thinks this never happens can't ever have been even a bit fat. I've had it happen at size 16 (was never any bigger) - it must be so much worse for those bigger than that. I'm two stone lighter now and it's stopped happening.
Saying it couldn't happen is a bit like telling a black or brown person "Yeah, you should totally go on holiday hill-walking in one of the most rural and white bits of the UK - there's absolutely no way you're going to get any of the locals looking at you like you've got two heads". They might. Denying that crappy behaviour ever happens, to the people on the receiving end, is not helping them. They should still go, obviously, if they think they'll love hill-walking. And ignore any idiots. But it happens.
Go. Dress glam. People respect you more when you look like you respect yourself. Get your hair and nails done and maybe think about waterproof make-up. Remember that size 16 is not size 30, and you don't stand out as much as you think you do. (A lot of people who've lost weight can't really "see" themselves as the size they now really are). Have fun. Maybe you'll get some skinny orange bird with too much lip filler raising an eyebrow, but probably not, and who cares what people like that think anyway? Remember: you're not even that bloody big. There's nothing actually the slightest bit unusual about the sight of a woman who is your shape. It'll be fine.
Remember to report back on how much fun you had!