Not sure which point your coming from, from a young person surrounded by older adults or an older adults surrounded by younger people?
As for a scary place, nope no way not even miles close to what you find at any all ages shows at any night club.
Let's be real, are you worried about hooking up with an underage person? I and every adult over 18 has that in the back of their mind. One thing that always calms that is a simple question. "How old are you?" Now depending on both people their answers will come down to their own morals or goals.
If all you want to is dance and have a good time, age is not a factor. And there is zero to worry about.
If you have some ulterior motive that includes dancing and hanging out at the dance then I hope both people have the common logic to make the right choices. Fanime can't tell us how or to whom we should have fun with.
With that said it's up to everyone to look out for themselves. But I get it if your 18 or younger you don't want some 20 something hitting on you, or do, I'm not sure these days. This is a touchy subject after all. Guess what I'm trying to say is don't be a creep, stop trying too hard to hook up with someone at the dance, or if you feel some person is being too creepy tell then to stop, if they don't get it ask staff or security. There will always be creeps regardless of age group.
In all my years going to Fanime and going to the dance (I still find it silly people still call it that) I have yet to confuse the age of a girl for a minor. Then again I don't go looking to hook up at the dance. /humble brag.
Mod edit: its called a dance