I am a retired Physical Therapist. He may have vision issues or balance problem. Have his doctor tests his balance and possible vision referral to a pediatric eye doctor. This is the age where eye-hand problems become apparent. Below is a good information web site to help us ID problems. Check it out.

first, my daughter used to be like him she used to sit on the bike or swing waiting for my help .... then by age six she didn't know how to swing herself one day i left her without help she started to cry then she moved on the swing and learned to swing her self alone.

He's too young for pedaling.  Try a scooter first - great for balance and confidence building while in movement.  As for balls, have a selection of balls.  There are soft balls and foam balls that are easy to catch without any bumps.  I've found some 5" ladybug patterned balls that roll and bounce and can be easily played with.  You can roll things through a little obstacle course, play "hot potato" with just rolling back and forth together between your four legs -- all very simple and playful games.  When he's ready, he'll do more.  

Here's a link to some articles on my website about movement and learning that might interest you.  Best wishes, and happy playing!