K.C.
I think 5 is a good age to let her choose her friends, rather than having to invite everyone in the sake of fairness. Plus, since she is a summer baby, it helps that you don't see the preschool kids all day. I would invite the 8-10 she wants and keep it at that. Simple is always better!
As for the ones you don't invite but are friends with on Facebook, I always try to avoid posting pics on FB if I think people will see them and feel bad that they weren't invited. I didn't post any pics from my son's party this year, just ones from opening presents and stuff at home.