I am only really concerned about making one of the drives a loop around the lake. I know there are a lot of things to see in VC and Reno as well so its just a matter of what do we want to do as a group, what do we want to do as individuals and what works best as smaller groups. I know this is a group gettogether but there are lots of quick things in VC at least that my wife and I want to check out/visit/walk through/etc.. These may work best in smaller bunches rather than a large group.
What kinds of things besides route drives can be done by larger groups in the area? Im sure there is probably some kind of boat tour on the lake that can be arranged?
What about meals? Lunches will probably be a picnic type, or grab and go affair, but what about dinners? I tend to be a spur of the moment type of eater so pre-planning usually doesnt work out with me, but I am usually up for joining the rest of the group as long as I can find a menu item that interests me (steak is always a good fallback meal served pretty much everywhere so im usually good pretty much anywhere). Breakfasts will probably be hotel affair.
What time of day do we want to start things up? I love sleep so before 8-9 am makes me grumpy. It is a vacation too after all.

Im not against planning the day out over breakfast, as long as it doesnt take forever and we have a good chunk of options of places to choose from.

One last thought. Long days filled with just sitting in the car tends to make me irritable and can give my wife pretty bad migraines. Basically a nice couple hour drive coupled with plenty of walk-around sightseeing time is a great idea. Plenty of picture stops is great as well. I know the gathering is about our cars but, i drive mine every day so i would rather focus a bit more on the people and only a little less on the cars.

Just my $.02. Take it for what its worth.