Not to be a kill-joy but there is always the possibility of inadvertently spreading Sallmonella to the folks that handle them during a visit.
There are a lot of nice possibilities in the way of snakes though for such a purpose.
I once read that an entire class full of kids came down with Sallmonella after visiting a facility where they were shown a Komodo Dragon.
Some other folks might be able to give you better specifics.I used to do the "show and tell" thing for groups but stopped after reading about that. I wash my hands after handling my animals and just practice good hygene and have not had a problem. I hear it's not an uncommon thing for herps to carry. Nice idea though. Good luck.