I agree, and I have never asked the school to ban peanuts, much less tell others what to do in their home. What I did was leave several treats for my child in the classroom for the teacher. That way when someone brought in treats for the kids, my child got something out of his stash, and everyone was safe.
You can't ban substances people are allergic to, or you wouldn't be able to eat anything at school. But, a small child does need courtesy and cocperation from the adults in charge to keep them safe until they are old enough to take that responsibility on themselves.
I'm in full agreement. You are a smart cookie with advance preparation for treats at school.