Tuscany or Lake Como

Using ferries on Lake Como is a pleasant way to visit the lakeside towns and villages, easier than relying on buses in Tuscany. However, with a child, staying in a small city like Siena might work better. Lake Como is all about beautiful scenery. In Tuscany, I think you would find more to appeal to him.
Lake Garda has a beach, ferries and an amusement park plus would situate you well for getting to Castelrotto so it might be a better option than Lake Como. Look at Malcesine with a beach and a castle.
Has he been to Venice? That might be a child's favorite spot and also works well for getting to the Dolomites.

For much of Tuscany, you will need a car. Have you asked your son what he would like? Maybe watch youtube videos on different areas.
Since you have 8 days, have you considered Rome? So much to see and do, and lots of easy day trips.
Or, if you don't want to travel that far, Bologna (food), day trips to Parma (Parmigiano cheese factory, Parma Ham factory).
Lake Como is relaxing, but a 10 year old might get bored. But, then again, I don't know your son!

There are guide books specifically aimed at things to do with kids. If you go on Amazon’s site and put “Italy with kids” into the search box, you’ll get some titles. My daughter found a walking tour and a cooking class that were big hits with our grandson.

With 8 days,I would think you could do both. I would base in Florence for Tuscany. Lots to do there!! You could take day trips to the countryside by bus quite easily. Land in Rome and then take the 90minute train ride to Florence.

For Lake Como, many here prefer to stay in Varenna; however with a 10 year I would think that Bellagio will have more to do. We actually prefer Bellagio to Varenna. Hands down. You can take the fats train from Florence to Milan, to Varenna and then ferry to Bellagio. You can ferrry all around the lake from town to town once you’re there.

Thank you for all your wonderful advise. As suggested, I was looking at using Florence or Verona as a base. But for some reason we started to look at Switzerland. My son latched on to the idea of visiting Berner Oberland. So we decided to spend 5 nights there, which would leave us 4 nights to spend in the Lake Como area. I suppose we will have an overload of Alps. Thanks again for all your help. You never disappoint.

No such thing as an alps overload. We love both the Lauterbrunnen valley and the Val Gardena (near Castelrotto).You can compare and contrast the transportation, scenery, food, and prices. 😏