Put them to work, make part of it their responsibility, tell them you need their help. I let my boy steer the boat a lot, I always have. I point him in a direction, a point of land, a channel marker, or a compass point and he'll steer and do it well. He helps navigate, checks the GPS waypoints and charts, blows the jib sheets when we tack, helps fix the boat, helps clean the boat, you name it.
He's 13, but he's a dwarf so there are a lot of things he can't reach but we keep him busy with things he can reach. I value his perspective and he has good ideas that help us all. His input is important and he's a part of the crew and I wouldn't do it without him.
And he can cook.