-shudders- Oh my, I got my braces in the 3rd grade and it absolutely sucked. Thankfully I only wore them for a year, but I hated them with a passion.
But anyway, go ahead! Cosplay with braces isn't a problem. If someone doesn't like it then they don't have to look. :3 Like CobaltTempest said you can always smile without opening your mouth.
I no longer cosplay.