This isn't in your question and you say he is ready but for other readers perhaps this would be good to know.
When my nephew was having a hard time learning how to ride a bike, my dad read up on it and found that using a scooter first was a great way to learn how to balance and propel a bike.
So we got our son a scooter and then later, there was a cub scout bike hike his 2nd week in scouts. Ohhh dear, we didn't have a bike nor had he ever been on one! Yikes. He went over to a friend's house and rode their youngest son's bike and in a couple hours he was riding (no training wheels) and the next day he went on the bike hike and did fine. So he loved biking and we got an used bike which he loves and is on whenever we let him!
So you moms with kids that struggle to learn biking, get em a scooter first. (Best of all, a new 'razor' scooter is only $40.)