S.F.
Being so young, I would get him a 3-wheeled scooter. I haven't been comfortable with my kids having a 2-wheeled Razor until they were 5. They seemed much more capable of controlling it safely. I don't know if they make 2-wheeled scooters that are intended for younger kids?
Get a toddler sized helmet. Take him with you and try them on so you know they will fit him properly.