Ha, the only thing worse than my mother inviting herself is my mother-in-law doing it

It sounds like you had a pretty nice mother-in-law! Your parents had some nerve criticizing the idea of a time share and then tagging along anyway.
I am just so tired of having to watch what I say to my mother all the time. God forbid I am doing something interesting -- she wants to come along. I try to remember this and just stay vague about my plans, but sometimes I slip up.