I guess if you were that hungry, you could do the bar first and then meet someone in the dining room later. You would need 2 receipts and 2 observations. The dining room isn't going to work for the bar audit and the bar audit isn't going to work for the dining room.
But sure, if you want that much food or want to be there that long, I do not see why you couldn't do both on the same visit. It's not like you are trying to get paid twice for one set of info. You are doing both scenarios on the same visit and they have nothing to do with each other.