Look for a simple, natural background that adds soft color and gentle lines to your composition, but doesn't detract from your subjects. Even if you're miles away from blue horizons at the beach, the great outdoors offers many other beautiful options: a green lawn, a lazy river, a football stadium, an amusement park, an old barn, or a stone wall. Look for color, simplicity and a spot where your family will feel right at home.
Keep an eye on what's going on behind your subjects, too, so Grandpa doesn't appear to have things growing out of his head. Eliminating a distraction can be as simple as adjusting your camera position.
Remember to set your camera with a shallow depth of field to slightly blur the background, keeping the focus on your family.