I wouldn't worry about finding a place that sleeps 13-14 if you choose to stay in Varenna. There are places next door to one another, or down the street. People can still meet on the patio for breakfast, by the lake for picnics, etc. Three generations aren't going to go to sleep or awaken at the same time anyway. You'd need something like Hotel Grand Serbilloni in Bellagio to sleep that many.