I sympathize and I've been there. But I think you need to re-write that letter substantially.
If I were you, I would focus - gratefully, humbly! - on the outpouring of support and generosity you have experienced from these folks before getting into what you want.
Also, worst-case scenario, you get some crap you don't want -- you either return it and get stuff you do want, or donate it to a charity that will give it to people who could really desperately use it. Really, that's not so bad either way!
Since I am pro-registry (as long as it's being given out only to people who ask for it, of course!), I think it's best to be as specific as possible. The online registry is a great idea. From your list, Bena, I think you could be a little more specific on some things:
-items to make breastfeeding or cloth diapering simpler (we have already selected cloth diapering system by Mother-ease, a locally owned, environmentally friendly business)
-books and music to stimulate imagination and curiosity
Likewise, I doubt anyone deliberately sets out to buy books and music to suppress imagination and curiosity. So if you have specific products in mind I would let people know what they are!