JEAN, a few thoughts to add to Kent's always excellent information.
First of all, a bit of further information would be helpful. I'm assuming your group is 5-6 couples, so that's the number of Hotel rooms you would need? Also, are you only going to be travelling to Lago di Como, or elsewhere in Italy?
A tour is certainly one option (depending on your budget(s) of course), as someone else does all the work in figuring out transport, hotels, meals & local tours. If you were going to consider that, I would highly recommend the RS tours.
As Kent mentioned, some of the roads in that area can be somewhat "challenging" for drivers used to wider roads, which may be more of a concern driving larger vehicles like Vans. With accurate planning, there's no reason not to use public transportation, even with a group of 10-12 people.
The first thing to do is decide which town you want to use as a "home base" on Lago di Como. I think it's safe to say that the majority of Rick's readers would suggest Varenna, and that would be my recommendation also. As far as lodgings there, one possibility to consider would be La Torretta B&B, which is managed by Laura from Hotel Olivedo. I hope Rick doesn't mind, but to quote his recommendation regarding the B&B - "This would be an awesome little palace for a party of 10-12 to take over" (Italy 2008, page 215).
One thing to keep in mind regarding the trip you're planning this time vs. your previous trip to Tuscany is that the situation is somewhat different. At Lago di Como, you'll be travelling mostly by boat to get around, rather than using a vehicle between towns in the area.
How many days were you planning to stay in the area, and which sights on the lake do you want to see? Also, even though one of the group is fluent in Italian, it would be a good idea for everyone to learn a few common words.
I'll wait for some further information before posting any more suggestions.
Cheers!