I also love even strong winds, in the rare time when Bora (NE) blows I'm ready with my shortboards.
About my lagoon, the windsurf SHOULD be allowed outside the channels. I say should because as usual in Italy we have tons of rules and laws, and thousand of people trying to do the opposite...
That's a good reason (also because of hot temperature) why last three summers I went to Denmark to have windsurf in a free and cooler country.
The main rule says that in the shallow waters outside of the channel you can do windsurfing as I commonly do many times, and in the opposite it is forbidden in all the channels, even if I must confess that sometime I also quickly cross the channels, depending on the wind..
So you have a lot of nice and sometime stil almost wid zones, especially in the northeast side of Venice, but also in the middle-south, the only thing is that is better to stay far from Venice and his port.
The only problem could be the accessibility, as told I carry the Queen over my traditional boat and go far from Venice. So if your friends live in Venice watertown they should do the same with a not too wide boat (wide boats are not allowed to go in the muddy "barene"). If your friends live in the outskirts and mainland (Mestre) you could consider to reach the edges of the lagoon with the car, but keep in mind that also the rules for carrying a long thing like the Queen over the roof are here not easy like in Usa, so a car long or not much shorter than the 460 cm of the Serenity is better.
Last things, a raked seaweed dagger-fin is necessary, and for longer trips a sup paddle to carry over the deck it's a good idea.