Happily, I hadn't seen your letter when I was posting - we were posting at the same time. I think it's a good letter - the one small thing I'd do differently (which is only me - I'm not a professional advocate *and* I am a scientist so writing letters is not my strong point! - so take my advice with a grain of salt!) - is to add an exact description of what your ds told you:

For example:

Dear Ms. Teacher,

DS told me that during Writer's Workshop ____ fill in the blank ___ happened. I would of course also like to hear your perspective on what happened to. I beleive you may have seen.... (leave rest of letter as is).

I really do think you put together a great letter smile

polarbear