I ask my daughter rather than tell her.
Luckily she is a nice child and that almost always suffices. Practically every sentence she hears me say contains a please and/or thank you.

You can ask a child politely to do or not do something whilst still making it clear that it is really a command.
( Monty Boyce, My cheese game is strong, Mon 23 Jul 2012, 10:22, 2 replies, latest was 13 years ago)

This^
Politeness costs nothing (fortunately for you)
( sporters I’m sincerely gratitude to you, Mon 23 Jul 2012, 10:22, Reply)

Agreed
My kids are only told to do something if they are about to hurt themselves. Though most of my asking comes with a threat, i.e. She-Ra pick up your toys please or I will have put them in the bin.
( Peej, Mon 23 Jul 2012, 10:50, Reply)