Welcome to the site!
By now, you've had a wide variety of intelligent input from our members, but still, I'd like to add my .02 worth.
First, a CVO is a huge investment, and even though I like the fact you want to surprise him; in the end, you may want to involve him in this process because:
Secondly, it's a very personal investment also. The 31" inseam is only a small part of the considerations one makes when buying an expensive (and powerful) motorcycle. The weight of the bike, his riding skill level, do you want to ride with him?, will you be only taking short trips around town or going for longer "touring type" runs, the color, the year, the cost, etc. The list of questions goes on and on.
Even if you find and buy a used CVO, you will still be spending at least $10-15k on the bike, and that is a huge investment for what might end up being a regret in the long run.
My advice? Take him to a dealer where he can sit on the bikes, then do test rides on a variety of bikes. If there's one that he falls in love with (for color, size, type, touring or not, etc.), he'll let you know. Then make your decision on whether to still surprise him or not.
Good luck!