Some of us have a hard time taking directions but are very good at being bossy. Ask your child to help you learn to play part of a piece they're working on right now, or just sit down and start noodling around on the keys. Presumably you will make many errors, possibly even starting with your hands in the wrong position, getting the rhythm wrong, forgetting the sharps and flats, etc.
You will have so much difficulty that you'll probably have to ask your child to point to the notes for you as you try to play it, to sing the song with you as you play it, to record the song for you so you know what it should sound like.
Often times they'll end up frustrated with you and just want to sit down and play it themselves.
(Read between the lines on the intention of this activity)