when I only had 16 acceptances and one of those contacted me earlier in the day to say their dd was ill and couldn't come. That means 7 people who never responded turned up. Obviously they were welcome but just unexpected!
Luckily I'd made 25 party bags and catered for plenty as I always like to have extras for siblings if they turn up at pick up time for example so we had enough but AIBU to have wanted to know in advance?