The solution for you can be find accommodation for your luggage only for a few hours.
The places where you leave your suitcases guarded are:
-Our office Grimaldi Apartments keeps luggage free of charge
-Venice Luggage Storage in Calle della Malvasia near Rialto prices vary from 5 to 10 euro per day
-Keep Calm Point is the luggage deposit of the Venice station prices vary between 5 and 8 euros and is located alongside the track 1
-Luggage is the first company in Venice that has dealt with the luggage storage The seats are at Tronchetto, in Piazzale Roma and at the station. It also offers several other services: