Wow you guys are really running a serious production. It looks like we're in for a real treat here.
Regarding the restriction on races during character creation, I have a similar issue as I (for reasons of lore) don't want people to create neither lizards or undead. My approach to preventing this is much simpler, I'll just put in a disclaimer telling people to please refrain from making a lizard or undead character.
Check for the tag when they load into your first level and boot them back to the main menu to try again if they don't behave.
