Unfortunately, all of the Venice attractions are out on the island of Venice. You can find a hotel in Mestre, which is the town on the mainland just before you cross the causeway to Venice, but there isn't much to see there. The distance from the Mestre train station to Piazzale Roma, which is the end of the line for land vehicles in Venice is over 5 miles. Just the causeway itself from end to end is over 2 miles although there is a sidewalk. If you decide to stay on the mainland I would recommend taking the bus or train out to Venice and spending the day there. It would be better to find a place in Venice to avoid having to go back and forth every day.