A couple weeks ago, my girlfriend and I had dinner over at my parents house. Everything went great and she really enjoyed meeting my family. So much so that she immediately wanted me to meet her parents (who live 4 hours away). She had a dentist appointment scheduled for this weekend (with her regular dentist - down at her parents home) so she asked me to come along with her. I happily agreed. So... we'll be staying at her parent's home for the entire weekend. My question is, assuming everything goes smoothly, how appropriate would it be, once I come back home, to send a Thank You letter to her parents for letting me stay in their home? Remember it would be the first time I have met them. Also if anybody has any advice on the actual meeting of parents, I'm all ears. This is the first time I've ever done this - kinda nervous.