For "giant geckos", I'm assuming you meant Leachies. If so, then they are pretty chill and their husbandry isn't too bad. I wouldn't advise any large day geckos as their skin can be harmed if handled incorrectly.

I'd also advise against the chameleon.. Unless you find a VERY chill one. They stress easily and handling often isn't advised.

Other than that, I think your other snakes sound like good ideas. You might want to consider adding something flashy like a rainbow boa. Also, maybe something different like a sand boa of some sort. They are laid back and burrrow into the earth, which would be good to show kids (different environments, etc.). Plus, it would be pretty cool, as a kid, to see an "empty" tank with sand wheeled out then see someone dig a big sand boa out.

One thing you didn't mention is if these events would take place elsewhere (you would travel) or if the people would come to you. If they come to you, animals like the chameleon might work as that would be less stress on them... You could show the chameleon feeding on insects in that instance too.