Not too ambitious - fantastic trip. We've done similar (but only there and back) to Italy, but it's a long time ago.
When are you going? Outside mid-July/mid-August would be best, to avoid full campsites. Also, you can use an ACSI card, or Camping Cheques, meaning that a night on site for two people, caravan and awning, pitch and electricity costs only 14 euros. See their websites for details.
We stayed at Camping Eden on Lake Garda - but not good for twin-axles (tight bends). We don't have a twin so will leave site recommendations to others.