I had gotten a scooter for my oldest at about age 4 or 5. It ended up collecting dust.
At about age 7 I got my boys plasma cars. They're also called wiggle cars.
We had gone to a big party in a barn where there were 3 of them and the kids played for 4 hours, zooming around on them, non-stop. Even the littlest ones...2 or 3 years old...were able to enjoy them. They're able to hold 220lbs, so the adults played on them too! They're so fun...you wiggle the handle back and forth, and the car MAGICALLY moves forward or backwards...without your feet even touching the ground.
I found them on ebay in a 4-pack and bought them. The kids and I get on them and play bumper cars, chase eachother around, and have a great time. They're FUN.
This is what they look like (they're VERY sturdy, we've had ours for 5 years and they still look new): http://www.plasmacar.com/
You can easily find them on ebay for a great price. Be sure you get one for each (and one for you). It's way more fun if everyone has one.