What to do in Venice
 

Looking to see if there is three days worth of things to do for a 18/21 y/o and Mom in Venice. The 18 year is super reluctant to go, so hoping to find a cool tour or off the beaten path stuff. He'll have had his fill churches, museums and architecture.

Is your 18 year old someone you cannot/don't want to leave at home? I had a 16 year old who felt no value in going to Europe over hanging around with usual friends, so we left her with a guardian. Now that she has to pay for everything herself, she now kicks herself for letting go with an opportunity to go to Europe on someone else's dime. She doesn't even remember what she did while we were in Europe. This could not have been a better life lesson.

It would be a hard sell if one chooses not to assign value to the experience.

How about a gondola rowing lesson? Google it and you will find several offered.

Biking. There are several bike paths and you can rent bikes. Maybe along the Brenta Canal.

If you will be there on Friday or Saturday night in summer, they could both head over to the Aurora Beach Club on the Lido for music and dance.

Warm weather, afternoon at the beach in the Lido.

What a bad mother you are to impose Venice on a 18 years old.

Give them each 25 euro in the morning, and tell them to get lost. Venice is a great town to just explore.

Athletic? Kayaking in Venice: https://www.venicekayak.com/
Into music or clubbing? http://www.worldtravelguide.net/venice/nightlife or head to Mestre
A view from the young alternative crowd? http://www.roadjunky.com/guide/italy...ly-just-magic/ or do some reading/searching on http://www.travelpunk.com/
Into a university town feel? daytrip to Padua
Drinking? At age 18 he's well above minimum drinking age