A.M.
J.,
I have been a dental asst for 8 years and this is VERY common in little kids. Teeth are "new" to him. He is discovering his teeth just like he discovers fingers and toes. I bet 80% of the kids we see grind their teeth. Almost all grow out of it. He is so little I dont think there will be a way to stop it right now. Baby teeth arent THAT important (we lose them) so if hes still doing it when he has permanant teeth you might need to get him a mouth guard. Right now I wouldnt worry about it. Now as far as your husband doing it , he might need to get a night guard, grinding in adults is stress related and he can do damage to his teeth and stress out his muscles in his head and neck .
Hope this helps! Good Luck,