If you are lucky enough to have a swimming pool in your yard, you might also consider a pavilion or structure adjoining the pool area to provide some shade from the sun.
Casual furniture, TVs and video consoles, sound systems, even fans and misters are amenities that can be added to your shade structure. Board games and playing cards, and a snack bar with a fridge for drinks and a microwave for popcorn and other snacks will do a lot to keep the teenagers around, and a breezy, outdoor room might be just the type of space the kids will take over for the summer. Even without a pool, an outdoor room can provide the entire family with a comfortable place to gather in the dog days of summer.
On the other hand, a casually appointed outdoor room might be a perfect escape for the homeowners, stocked with books, movies, and comfy, overstuffed furniture.