Teacher/Student friendly Avatars

Hi - A teacher colleague of mine discovered Voki avatars (http://www.voki.com/) and had a blast creating one and embedding it in to her 5th grade classroom wiki. It allowed her to create a very nice and appropriate avatar in addition to allowing her to record her own voice. She used this to give directions on the various classroom wiki pages. No sooner had she added it when a student figured out how to go to Voki herself and sent her back one that she had created.. not a bad thing except that the Voki website offers games and other "voki" type adventures that are inappropriate for young students. The audio avatar itself is awesome but I've been having a hard time finding another product (free, preferably) that does the same thing without connecting to inappropriate content.. Anyone out there come across anything like this? Thanks!
Donna