I love pergolas for creating the effect of separate outdoor living spaces on a large deck or patio.
They have a way of defining a separate outdoor space without closing things off. So this way you can still watch the kids while relaxing, but be a bit away from the noise and activity.
The idea of different activity areas is just like inside your house where you have different rooms for different activities. But outside there are no doors or real walls so we need to create distance without closing things off to the point you are no longer feel like you are really outside.