Events on Lake Garda

With just one day, it's best to focus on the lower lake, where distances are short and everything is well connected. This route keeps Sirmione for the morning, when it's least crowded, and ends with a sunset over the water.
Leave the car in the car parks before the peninsula and walk in. The Scaliger Castle and the Grotte di Catullo, the Roman villa at the tip of the peninsula, comfortably fill two or three hours; in between, a walk through the old town.
Have lunch in Sirmione or move to the Verona shore, to Bardolino or Lazise (20-30 minutes by car). Alternatively, boats and short cruises leave from Sirmione's harbour.
Bardolino for the lakefront and a wine tasting among the vineyards; Lazise for the medieval harbour and Scaliger walls, with fewer crowds. Both have equipped beaches if the weather invites a stop.
End the day with an aperitivo on the Garda promenade or at Punta San Vigilio, a small peninsula with a historic inn and a bay, one of the finest views on the lake at sunset.
It's difficult: Malcesine is on the opposite shore and at the far north, at least an hour and a half by car just to get there from the lower lake. Better to give Malcesine and Monte Baldo a second day.
The car is more flexible for the lower lake. The boat makes sense if you want to relax and see the lake from the water, but winter timetables are reduced.