I really hope everything is going well for you tomorrow night. However, are you sure that's what your girlfriend want? One earlier post already mentioned it, and I seconded it. I know all the guests you've invited are close friend, but it won't make any differences. If she is a shy person, she will feel embarrassed anyway, it doesn't really matter who sit around her.
Anyway, it's your proposal, it's doesn't matter what I think. Again, hope everything is going as planed! And good luck!