Originally Posted by
Coltybear 
My "little" sister (she's 27) is coming to my house with a new boyfriend Saturday night. The expectation will be to drink and hang out.
Who's expectation? Theirs? Or yours?
And who's to say you have to meet someone's "drinking" expectations. There are a lot of non-drinking things you can do that support, and might even enhance, meeting the sister's new bf.
Pick one.