Ok gang, I need some advice or something...

[here_is_to_hope]

I have an 8 year old daughter, relatively bright, very aware, reads wikipedia for fun. Trouble free except for recent rants about what a 'farce' God and religion is.
We live in a small town, she has had zero personal exposure to any GLBT people but understands what those terms define.
Well, this weekend, we will have an openly gay couple staying with us for two nights as part of couchsurfing.com.
She gets that girls can like girls, boys can like boys, that gender identity can be
confusing.
She will want to ask questions, I know it. Apropriate or otherwise, it's her nature to be curious and outspoken.
Should I be proactive and talk to her about what she may ask and what she may not? In general terms?
Or should I just warn my visiting couple that I have an 8 year old who is going to be giving them the once over?
I doubt she would offend any one but she might cause some discomfort.

Thoughts?