I hope I don't have a problem on my hands [DM issue]

[Gecks]

Maybe ask him specifically to be the "wise old man of the party"? Something like "Hey, I know you know the system in and out, I was wondering if you wouldn't mind either making a unoptimized build or choosing a "weaker" class so you can stay in the background, you know, kind of deliberately keep out of the limelight and whisper in the ears of these noobs about how the game is played. That way, they'll think they're kicking A** and taking names on their own, and they'll have fun enough fun to become die-hard players themselves. It can just stay between you and me about how much of their success is actually on you- at least, until the next campaign, when they won't need hand-holding and you can build that world-killing wizard you were thinking about."

It may have just been my own good luck, but I've recently started a campaign with a very wide "player experience" spread, and personally I've found using the vets to teach the newbies has been perfect- the vets actually step back and let the newbs shine, and the newbs seem to take advise better from fellow players instead of the DM. I've actually seen vet players with (relatively) optimized builds actually step back and let the newer players take over when they happen come up with a good plan or a neat idea- when initially I was worried that the exact opposite would happen. Just a thought.