I agree and disagree at the same time!
I certainly think you're right about the kids getting dirty thing.... kids are meant to play in the dirt, it's their job and it's how they build up their immune system.
The thing about pathogens and parasites in captive reptiles, is that the populations can 'explode' in a captive environment. Also the increased stress levels of captivity can lower an animals resistance to illness.
I believe their is a balance, use wild caught prey if you must. Just be aware of your snake's behaviour and watch for subtle changes.
Captivity is obviously an unnatural state... there can be no perfect or problem-free way of doing it.