I've never been to lake como but lake garda is one of my favorite places. Lago di Garda as known in Italian divides the regions of Lombardy, Veneto and Trentino Alto-Adige.
The large lake is long and slim, stretching from north to south. The southern lakeshore is low, rolling land and fairly built-up. In contrast, the dramatic fjord-like northern end (Riva Del Garda) is surrounded by towering mountains and cliffs. Most of the lakeside towns are popular as holiday resorts.
Not to forget the many attractions offered around the lake that will keep children happy (if you have them) such as gardaland, movieworld, Canevaworld (waterpark), etc....
Lake Garda has attractions for all ages.
Tip: Avoid August if you can as things get very busy.