I agree. The less you say, the better. "Petunia and Cuthbert are registered at XYZ and ABC." Period.
Don't go on and tell them what you're hoping for most or graciously agreeing to accept. Definitively don't try to "give him them permission" to "go off registry." No one has to buy from the registry in the first place, and the more you protest that you are fine with gifts of their own choosing, the more it sounds like you really aren't.
If you'd rather have cash, for a honeymoon or anything else, just don't register for much (or anything). People will ask you or your parents or friends, and then -- because they asked -- it's okay to answer that you/they are trying to save for a honeymoon/car/house/whatever.
Whenever you find yourself struggling too hard for wording that won't sound greedy, tacky, or pushy, there's a very good chance the problem isn't the wording. There's just a limit to how far you can go, politely, to control others' generosity toward you.