Curt,
How old is your boy?
I once went to a coaching clinic and got the best parenting advice I've ever received when it comes to kids in sports.
The three best things a parent can do/say when a kid is in any sport are the following:
1.) Provide them with opportunities to do what they love (or try new things).
2.) Tell them to have fun.
3.) Tell them how much you enjoy watching them have fun. (Unconditionally.) Sometimes this might mean feigning ignorance as much as possible.
Because I coached runners, when my kids played soccer I was the dumbest soccer mom out there. I knew nothing about the sport, and made sure it stayed that way. As a result I was never critical, never "worried" about whether they were having fun or getting beat. They didn't have to satisfy my competitive urges or live for my approval.
Likewise, it allows them the joy of telling you what they know, and to grow masterful at it.
Anytime you are more worried about your kid getting beat than they are, you know your priorities are getting slightly out of line. It sounds like your little guy is evaluating his options on his own on how to be competitive and that he IS having fun. As Mox said, leave it up to him. If you over orchestrate it, you are living your own competitive desires through your kid. You should maybe just saddle up yourself and get that out of your system! It's not too late for you to start racing.
As long as you are giving him opportunities to both train and race, you are doing your job! He's lucky to have such an interested parent. He'll be fine. It's a helluva lot of fun, whether you are first or last. I'm guessing it is pretty much addicting enough on it's own level he won't get too discouraged.
Lastly, If you are determined to "help him" there are other ways to structure goals without getting too hung up on winning or even place. The skills are everything. As he masters the skills he'll become more competitive. Sometimes it's about catching the guy in front of you, sometimes it can just be about riding to the best of your ability. Don't rush him by getting hung up on place. Let him develop. Undoubtedly he's already hooked. I think if you got out there and did a bit of racing yourself, you wouldn't have so much restless energy to worry about his starts. Your adrenaline will be spent on your own races!