Fernandina Pinball Museum charges $14 for all day or $10 an hour. The owner mentioned he has to put prices on some games, since I guess as far as the city is concerned, it's a sales showroom.
I think they have a big table and some chairs in the back for parties.
Your hours seem kind of short. Longer hours are more attractive to me when I'm driving any distance. Leagues and tournaments are a definite draw.