If I buy the Vaporetti Pass, does that also cover the trip on the Alilaguna Water bus from the airport to my stop in the Grand Canal?
Unfortunately, no. Alilaguna is a separate system and requires a separate ticket.
However, the vaporetto pass is basically an ACTV system pass. It would cover the orange ACTV bus from the airport to Piazzale Roma in Venice. You would then transfer to a vaporetto for your trip on the Grand Canal.
Validating your pass at the airport as you board the bus would start the clock in the pass.
Vaporetto Passes and single tickets are NOT cheap. Minimize your Euro expenditure and try to do all of your necessary vaporetto rides in 1 day if you can.
Consider the VeniceConnected card for ACTV airport bus and discounted passes for vaporetti. Purchased in advance, this may be your best bet. www.veniceconnected.com/
We also used Venice Connected. The earlier you buy the pass, the better price you receive. My only caution, is to verify pick-up points for the pass. We picked ours up out front of the Santa Lucia train station. Make sure you can pick yours up at the airport if that is the first place you will use it. An additional note on Venice connected..... we bought several passes with the site and expected to pick up an entire packet on arrival. In reality, you must go to the site that the pass covers to redeem your reservation, i.e. the San Marco Plus pass must be picked up at one of the participating museums. And the museum pass was not discounted. The price for the vaporetto was worth it though. Hope this helps.