That should be a blast! Kids don't usually have the prejudices against snakes that many adults have---unless their parents have already indoctrinated them. It's fun to get them excited about the animals, teach them interesting facts and make them aware of the true value of snakes.
I can't wait for the Minnesota Renaissance Festival---which starts this weekend. I'll be out there most Sundays through the end of September, in Renaissance garb educating people about reptiles. I've always brought my corn snakes, and this year I'm bringing Loki out there for the first time (I thought he was too young to handle all the crowds last year).
It's the Minnesota Herpetological Society's biggest fundraiser of the year (and definitely puts the "fun" in fundraiser). It's hard to keep from laughing when people ask "is that real?" when your snake is actively moving around, flickering his tongue.
Let us know how the fourth graders respond to Jack and his posse. Definitely post pics! (I'll try to post pics of the Ren Fest too when I can, but I can't use a camera while I'm working since they didn't have those in the 1500's...) 
>>Oh, btw, I will be taking Jack to my son's 4th grade class next week. The other night I went to his class's "open house", and the teacher started talking about the kids getting a class pet. When he mentioned that many wanted to get a snake, most of the parents seemed surprised/disgusted, and one even asked, "Why a snake? Where is that coming from?" I raised my hand, and when the teacher called on me, I said, "Probably my son." Anyway, the teacher practically begged me to bring in my snakes to show the class, which I think is great. I'll try to get some pics.
>>
>>Thanks,
>>Ed
>>
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Renee
1.0 BRB (Loki)
2.0 amel & anery corns (Foxfire & Daguerre)
0.1 blood python (Duchess, arriving later this month)
1.1 Cats (Nightshade & Cuzzy)