Your best bet is to take the bus from the airport to Piazzale Roma and then use the Vaporetto to get to your accommodations, which look to be very close to the San Silvestro ferry terminal. You can buy individual tickets for this or they sell a multi-day combo ticket that includes unlimited use of the Vaporetto. A 2-day ticket costs 30 euro and a 3-day ticket will run you 40 euro. For an extra 6 euro they will add a single bus trip from the airport, 12 euro for a round-trip. Seeing as you are leaving for a cruise I would think the single trip option would suffice. So, for 36 euro you can get a 2-day unlimited use Vaporetto pass that includes a single bus trip from the airport to Piazzale Roma, where you pick up the Vaporetto.
If you think you will be using the Vaporetto a lot to get around while in Venice this would be a good option. However, most visitors find that they simply walk to get around while in Venice and use the Vaporetto only for getting to and from Piazzale Roma when arriving and leaving Venice. Seeing as an individual 75-minute Vaporetto ticket costs 7.50 euro, the 2-day pass makes sense only if you think you will use it 4 times or more.