Is keeping wild caught land snails Cepaea hortensis and Cepaea nemoralis found in the northeast USA hazardous at all to me or my child?

No it's not but, It is possible to keep some snail species as pets - there are only four I would recommend: Helix pomatia, Helix aspersa, Cepaea nemoralis and Cepaea hortensis. Any others are too small or have needs that are too specific to be recreated in captivity. See the section on Giant African Land Snail care, which can broadly apply to these species, except that the tank will not need to be as hot, and of course they require less space and food. If you found them eating a certain plant, provide it for them when they're in captivity. The advantage of keeping these snails as pets is that you can always return them to the wild when you do not wish to look after them anymore.