I'm not going to let my husband interact alone with our son after he's smoked
How do you define "alone"?
I'm going to watch them and then decide on that decision
It's good to protect your child from your husband if he smokes. You should protect your kids.
I guess, so why can't I do more to protect them?
It might not feel like enough, but keeping them away from smoke is good for their health. You should always do what you can do protect them.