Taking the picture from the child's perspective and having the family dive into a pool at the same time are creative ideas for a family photo. For an outdoor shot, simply have everyone lay down in grass or a field of flowers.
Taking a family photo out in nature gets the family out of a traditional photo studio, offering opportunities to make the picture interesting and creative. If there is a nearby flower field, the family can lay together or play and have the photographer take a candid shot. Alternatively, take the picture in the family's home. Have everyone in bed wearing pajamas as if they just woke up like that.