there is a luggage storage at Venice airport; no self-service lockers though (nowhere available after Spetember 11th, 2001). The quickest and more comfortable way to reach St.Mark's from the airport is through direct boat service, sort of taxi on water. It is expensive (no public service) but it takes your party from and to the airport on the quickest/safest and most scenic route. Otherwise you can catch the public transport service (bus to Venice then the boat down the Grand Canal) but it takes time and isn't very cheap too, considering you are a large group. I suggest you to visit the site http://www.veniceairport.it for more information and contact addresses. Enjoy your trip

Paolo Trieste, Italy