How many days for Lake Como and the Val Gardena do you recommend?

What time of year, and do you hope to hike? I'm asking because you might want to do some padding to allow for weather issues.

In addition to the charms of the Dolomites themselves, there are some attractive towns down in the valley (though potentially hot in the summer): Bolzano (with the Iceman), Bressanone, and Chiusa are among them.

I am going to be there (light hiking) 3 weeks late July - August 2021 if it is open to Americans for travel.