Just my two cents.... When I used to do nature programs, I used adult snakes. (That's what the nature center had.) They always went over well in part because they were sooo calm. Since young snakes tend to be more nervous and skittish, I'm not sure they're a great choice for a nature program for young kids where there will be a lot of noise and action (no matter how many times the kids are told to sit down and be quiet.) If some of the kids are apprehensive about the snakes anyway, a calmer snake would make a better impression than a nervous, skittish snake that keeps trying to crawl up your sleeve....