Hi Inga, it is quite difficult to get to Lake Como/Lake Garda without going over or at least through the mountains, you will have to plan a route through either Switzerland/Austria/France and all involve mountains.
I suggest you google routes, toll and non toll and choose the one that suits you best and as for stopovers you can do worse than use searchforsites.co.uk to plan your stops as all kinds of sites are catered for including both Aires/Sosta's/ and campsite of all types.
We have been 3 times and really enjoyed Italy but we also like mountains and the more peaceful areas, I had sunstroke real bad at Lake Como in July and every campsite wanted a fortune to stay on, in fact the car park we were on was £27 p.n. with NO facilities right on the shore of Lake Como.
I am sure others will give you the benefit of the experiences, so look at all the info before making your minds up, but most of all enjoy it. Toll Route[You must be registered and logged in to see this link.]Non Toll Route[You must be registered and logged in to see this link.]