Thank you for your invitation.
It’s very kind of you, but I’ve got a lot to do, and that can’t wait until tomorrow.
Enjoy yourselves.
It’s a good play.
I’ve seen it in a long time.
I haven’t been to the theatre for a long time.
I know, this play is a great success, and the tickets were sold out.
I’m terribly sorry but I can’t accept your invitation for Saurday night.
Perhaps another time.