I agree with Psam:
<< My son is seriously allergic to milk protein, and I would
 never consider asking everybody else to avoid milk on his
 behalf!  >>

My son also has an anaphylactic allergy to milk and milk proteins....we've
always just implemented a solid emergency plan and found a good preschool (and
kindergarten for the fall) that is willing to work with us to keep him safe
without changing everything. Our goal is to help him learn how to live in a
world with milk and keep himself safe ....while educating his teachers and
ourselves. It's an ongoing process but well-worth it.
And, by the way, most of the mistakes that have been made in our family re our
son's allergy, have come from us, his parents. We carry the majority of the
responsibility -- gladly -- and so from time to time we make mistakes. And
then, we learn from them!
Just my two cents!
Rose