Hi again, Debbie, and thanks for your reply with additional information.
If the grad would prefer a graduation celebration at home, I think this would keep it more simple and take his feelings into consideration.
If he's willing to have the celebration directly following the ceremony at your Country Club, I don't see why golfing must be involved, as you can just eat at the restaurant. It's a familiar place, probably easy for family to access, and if you like the food and the ambience, that sounds like a good choice, only if it's alright with the grad. We have a Country Club as well, and live in a golfing community, but we've had many family celebrations/dinners at the restaurant of the Country Club, and no golfing was involved.
Having food catered in, is also a good idea and if you have free reign with the menu, include items the grad requested, like chicken fingers, perhaps wings(?) and more 'sophisticated' foods you feel the older adults in the family will enjoy.
Why does it have to be an 'open house', with people coming by all day (if it is just for family? I know with the kids, they do this, and go from party to party/house to house). Invite the family back to the house for lunch/dinner, whatever time the graduation is over, and people shouldn't be coming in and out all day, so you know how many people and you know how much food to order.
In your area, if the grad agrees to go to a restaurant, I think a private room is excellent, and just keep it simple, if he doesn't want a 'big deal'. Most of the higher priced restaurants in Louisville have private rooms, but you didn't mention your budget. Carrabas is nice, and if the restaurant can accommodate your party in a 'corner' of the restaurant so you feel like it's just 'you', that could be nice.
I don't know how far Buca di Beppo is, from you, but, although they don't have 'private' rooms, the way they're set up, each room accommodates only a few tables; we had my nephew's graduation dinner there a few years ago (where I live, in South Florida), and it was great. Because the food is served 'family style', you can order a variety of items to satisfy all tastes, IF you like Italian food. http://www.bucadibeppo.com/locations/default1701.aspx
If there is a particular type of food you're looking for and/or you can tell me about how much you'd like to spend per person if you go to a restaurant, I can search further for you, with those parameters in mind. Also, remember that usually there is a fee to use the private room in a restaurant.
If you have found this answer helpful, please click 'Accept' and leave positive feedback; if you need additional information, please click 'Reply'. Thanks for the opportunity to be of help.