The Beast walks around and does photos in the library for dinner. I've done dinner twice, and the better experience was in the West Wing/Beast's bedroom. Not as loud, more intimate. You can request it at check in. Dinner is good. If you want that experience, go for it. I'd recommend using Touring plans reservation finder. Worked awesome for us.
If you don't think that experience would be important for your group, then do lunch. And if you want a jump on the crowds, consider a PPO breakfast.