Tonight with your 5 to 8 year old
The prompt
“Show me the funniest dance move you can invent right now, just for us.”
What to listen for
If they leap up without hesitation and go big and goofy, they feel completely free to be silly around you with no fear of being laughed at in a mean way.
If they laugh but hold back a little, they might want you to go first or join in, inviting them isn't enough, sometimes they need company in being ridiculous.
If they refuse outright, don't push it into a performance; let them direct instead, like "okay, you be the judge of my move."
What this tells you
How freely they let loose in this silly moment shows how safe they feel being fully themselves, goofiness included, in front of you.