[Dana Joy]

I guess I am just too much of a grammar stickler to understand this. Adding please to a command does not make it a request.
If a child does not understand something said with proper meaning, I do not start using an incorrect meaning to get them to understand, I teach them the proper meaning of a word.
If a child does not understand something polite, it is not an excuse to be rude so they understand, it is time to teach them the rules of manners.
This is not a matter of children not understanding subtlety, it is improper use of the word please to say that adding it to a command turns it into a request. I have very black and white thinkers in my house and they understood this.

I absolutely agree that there are "have to's" and "want to's" with children and that you should never phrase a "have to" as a request, but in American English, adding please to a command does not make it a request, allowing your children to think otherwise is setting them up for difficulty, because it isn't how the word is used. I see it as akin to a child still learning the language deciding that all animals are dogs, and instead of teaching them otherwise, you changing your own vocabulary to match the child's. It is doing them a disservice and underestimating the capacity of children to learn the proper meanings of language.