In reply to aaron_t:
August is a bad time of year, I was in Bolzano this afternoon - it was 30+. Cima Cap is a good choice, easy to get to (walk from Riva) but is long about 1200m of altitude gain. Colodri at Arco is short & easy. Sallagoni is a bit harder, may try that tomorrow as thunderstorms are forecast for the higher dolomites. Burrone at Mezzocorone is shady with a potential cablecar decent, may require a bit of a walk in from the train station. There are good bus links between Trento and Riva del Garda.