Thanks for the very comprehensive reply .Mont Blanc Tunnel.
You don't say where you are starting from! Assuming you are wanting safe, flat, easy roads, you would be coming down the main south Peage (A26, A5, A31, A6, St Quentin, Reims, Troyes, Langres, Dijon, Macon), take the A40 at Macon. This leads to the Autoroute Blanche and takes you straight to the tunnel. There is only one spot where you may feel a tad iffy over the height. The Passy viaduct. Check it out on Google and see if it's OK.
The other side of the tunnel is the E25 which runs through the Valle d'Aosta. Lovely scenery (no drops or heights!) until you leave the Valley. Stay on the E25 until you reach the junction for the A4 for Milano.
You don't say which lake area you are going to!
For Maggiore, d'Ota, Monate, Commabio, and Varesi you come off before Milano.
For Como and Lugano , come off just notrth of Milano.
For d'Iseo & Endine, come off before Brescia
For Garda and d'Idro, come off after Brescia
We are coming from Annecy on the 20th ish June and heading towards the quieter lakes in Italy. We have nothing booked as yet so given it’s approaching the busy holiday I think I may struggle getting onto sites on the more popular lakes .