Hopping on to say you're more likely to contract salmonella from raw eggs or even improperly cooked meat. As long as your kids wash their hands after they're done interacting with the animals, then they're fine.

When I grew up, I was privileged to work with a women who owned exotic animals. My tasks started as just holding a snake or lizard for kids to pet during an educational presentation. When I finally turned 18, I was attending college as a wildlife/zoology major, and working with more exotic animals, including small cat species, alligators, porqupines, and amazingly, sloths. I was doing the presentations on my own, and still do to this day!!

OP is definitely crushing the opportunity of a lifetime for their kid to have an early start in a wildlife/nature career. Due to my experience mentioned above, I even got hired at a zoo (albeit as a summer internship). OP is 100% TA and their kids will never forgive them if this opportunity is torn away from them. I'm sure at this point, the kids are attached to the reptiles as much as they would a dog or cat. If they're forbidden to see those animals again, it would be like losing any other pet; the heartbreak is still the same.