If your crew is constantly larger than 5 people it will not be too difficult to make a good wave with most boats. For a large lake with potential of big waves I would highy recommend 23' or longer. I have an SV230 Enzo and I am very pleased with it's performance in rough waters. It has an amazing surf wake on the port side and a good wave on the starboard. If I regularly had a large crew I would look at the 24 footer. The main lounge in the 23' Enzo is not overly spacious.
The MB B-52 23' boat might be a good choice. You probably would not have to add additional ballast with a crew of your size.