If there are teens and the parents are not gamblers, what would make them want to go to Vegas? I think there's things that would keep the group occupied and they could still have fun, but they would not be enjoying the things that Vegas is known for which makes it the destination people want to visit. We spent a week in Vegas right before the pandemic, but that was long for us. We usually spend 4-5 days and we're also gambling and drinking. I think 4-5 days could be too long for a group that's not out drinking and gambling.
Lots of suggestions here already but things that came to mind for me are Hoover Dam, Grand Canyon, rides at the Stratosphere and Circus Circus, High Roller ferris wheel at LINQ, any of the shows like the Cirque ones but some are more adult-oriented than others, wax museum at Venetian, shark reef at Mandalay Bay, rollercoaster at NYNY, hockey/football game depending on time of year, fountains at Bellagio, Eiffel Tower observation deck at Paris, flamingos at the Flamingo, volcano and Secret Garden at Mirage, neon light museum, loads of shopping at various points on the strip. Lots of these things are free too.
Another option would be to book a hotel that has a chill pool area - we last stayed at the Venetian and got a cabana at the Palazzo pool. Both pool areas were quiet and family oriented, a couple of kids around. They were not the day club/party pools like you'd find at other resorts. It would be a relaxing time to sleep in, do a breakfast/brunch, spend the day at the pool, and then do activities/dinner/show in late afternoon and evening. I still think there's better vacation destinations for that dynamic, but this could be enjoyable too.