Scooter

My guys had a little 3 wheeled scooter with Spiderman on it.

We got our guy a scoooter made for the younger kids from Walmart for $19.95. It had wider tires and was made to go slower than the regular ones.

My 5 year old received a Y-BIKE scooter for her third birthday, started using it right away and still uses it. We are about to upgrade, mainly because her two year old brother is eyeing it. :)

They are a bit pricey, you can get them for around $70 on Amazon.

We got the small kid Razr scooter for our 3 year old's birthday. He loves it and can scoot all over. It's like a tricycle scooter-two wheels in the back and one up front. DH has taken to scooting around the house on it, so it will definitely hold a lot of weight! My 5 year old nephew also likes it when he comes over, so it'll last a few years.
http://www.amazon.com/Razor-Kiddie-Kick-Scooter-Blue/dp/B...

You should wait a year. razer scooters are amazing, but they are a bit hard for the under 4.5 crowd. They do make a little kicks one, now that I think of it. They aren't that expensive. Maybe 25 bucks? Yes, I'd go with the razor jr. he'd probably get close to two years out of it, and then he can upgrade to a Razer A2 or something that will last for eons (and they aren't that expensive either).

Glad to see you went with the Razor. My daughter started riding hers last summer when she was 2.5. In June, she moved at a snail's pace. By the end of August, I couldn't run fast enough to keep up with her. She rode it to the pool about four days a week - 1/2 mile in each direction. Now, at 3.5, she is really well balanced on it. Your son will do great. Spend a lot of time practicing in the beginning and he'll be flying before you know it.