We have a rather long car trip coming up between Chamonix France and the Cinque Terra. What is the best procedure for bathroom stops? We have 2 young children with us.
In Italy, rest stops are indeed, almost always, huge complexes of restaurants, gas station, convenience store. Sometimes more than 1 restaurant per gas station. All of them will have reasonable clean bathrooms, sometimes you have to pay like € 0,50 to use them.
As long as you stay on the major highways, you will have no problems. It seems there is an "Autogrill" every 10 - 20 miles. They are right on the highway, signage well ahead, with easy off and on access. Good places to stop for an espresso, snacks and toilets. You are going through my favorite part of Italy, the Valle d' Aosta. Enjoy