substandard Let's not; let us not; I suggest that we don't. "'Let's go out and play," said Fred. "Let's don't until the rain stops," said Mary. Don't let's go now. Let's go tomorrow instead.
LET'S DON'T
Meaning of LET'S DON'T in English
American idioms English vocabulary. Английский словарь американских идиом. 2012