Hi Jackie
We have always been to Italy in July/August as we are both teachers. No problems with going then but campsites do tend to be quite busy and roads too, beware of the St Gotthard Tunnel on Friday afternoons at peak season - VERY busy.
We went to Italy in 2006 and 2007 towing a 7.2m 'van. In 2006 we went to Lake Como and then on to Venice. In 2007 we went to Rome and then back via Lake Iseo. For 3 of these journeys we have travelled France, Belgium, Luxembourg, France. South of Nancy we took the N66 through the Ballons de Vosge mountains - gentle hairpins only. After a halt at Cernay we crossed the Rhine into Germany, immediately before Switzerland, to avoid the centre of Basle. Then through Switzerland on their toll autoroutes and on into Italy via St Gotthard Pass or Tunnel.
This route is all autoroute apart from a short westward stretch along the N66. The French autoroutes are all toll-free but we had to buy the 2 Swiss Motorway vignettes, ie, for car and caravan. All of this route is quite towable. The St Gotthard Tunnel is 9 miles long so if, like me, you don't like tunnels the St G Pass is okay for towing as an alternative - we used the St G Pass going south in 2006 when a puncture caused us to arrive at the tunnel on the last Friday in July - BIG queues.
In 2007 we came back via the Brenner Motorway into Austria as we had had a car breakdown and the CC Red Pennant had only be able to provide us with a less powerful hired, tow-car.
We tended to break our journey by sleeping overnight at autoroute "aires" and we have did this in France, Belgium, Switzerland and Italy. We, also, stopped at Camping Chenefleur near Luxembourg and Camping Acasias in Cernay (SE France) whilst travelling the route via Switzerland.
My wife and I both drive and so we take turns on these long journey. We reckon that 50mph and 300 miles in a day is good going for us. In 2007, travelling south, we did Dunkerque to Camping Chenefleur in a day, stopped their 2 nights, drove on to Aerolo, just south of St Gotthard Tunnel in another day, slept there at Service area, and then drove on to near Rome with one more stop at a motorway services on route.
I hope this helps. I've reviewed all of the campsites we've used in the campsite search section of ukcampsite.co.uk.
I hope this is useful to you.
Tim