Getting outside is always great for kids. Getting them away from the TV and video games can be great for them. Take a baby for a walk while you push the stroller and get some great exercise. Why not visit a nearby beach and collect shells. Maybe even build a sandcastle. If you like being on water you could canoeing at a local lake. You could have your children make some extra cash and set up a lemonade stand.
Looking for something more outside the box? Stage a scavenger hunt, where you have to find something that starts with every letter. Create 3-d buildings using toothpicks and mini marshmallows. Enjoy eating them afterwards. You could even give back by visiting a retirement home and read stories to residents. The possibilities for your summer are endless.