I'm going to ask a friend to stay at a hotel one night for a mistake I (very stupidly) made
Did you tell them about the mistake before asking them to stay?
I'm not sure if I should tell them about it.
It's good to try and make up for a mistake, but you should be honest and apologize upfront. That way you can clear any tension that may have resulted in the mistake and enjoy your stay together.
Maybe I'll talk to them about it so I'm not as stressed next time.
You're right to think that you need to talk to them instead of getting stressed out. If it was your honest mistake I'm sure they'll understand it.