Lou and Janet:
I would suggest contracting your desired area a little. And if at all possible, extend your trip another few days. Going by car would be the best way to travel with 5 people, and you need to return the car to the same country you picked up in or large drop off charges will apply.
I would suggest flying into and out of Munich. There are great tourist sights that young men would be interested in, including Deutsches Museum, Nymphenburg Palace and Dachau Work Camp. It's a great, lively city.
Then go over to Salzburg, stopping at Hitler's Eagle's Nest along the way. It's a very popular city with great music.
You could then drop down to Innsbruck and Western Tyrol to get a taste of incredible mountain vistas and the mountain life. The region's beautiful, like Switzerland, but cheaper and easy to get to.
The Brenner Pass is just south of Innsbruck, and it's controlled access autobahn/motorway all the way to Venice. The city is just incredible and well worth the effort to get there.
Coming back north, you could go a short distance NW of Innsbruck into Southern Bavaria and catch Neuschwanstein Castle on the way back into the Munich area.
The reason I suggest this region is that the only long drive would be down to Venice, and the other daily drives are incredibly scenic and maybe 100 mile days. Roads are very good, and very easy to negotiate.