I think that it's important when advocating to keep three things in mind:
1) Know what your overall goal is, as well as the immediate goal that you're attempting to fulfill with a written request.
2) Be brief, straightforward and clear with written communications.
3) When there is a back history (explanation of diagnosis etc) that might by helpful to reiterate with the person you are writing, structure email by stating the question you are asking up front, keep it brief, and include any extra details that they might need to have in a "ps" section.
4) Don't try to be polite by saying things like "I think" or "I'd like". Be positive in what you are asking for, and request it, don't suggest it.
Re this specific letter, you've done a great job of writing down many things that you wish you knew or could get from the school. I don't think it's the right time to send the letter and I don't think the 504 coordinator will have all of your answers. My suggestion is:
1) Wait and talk to your advocate. Your advocate will help you get a firm picture of what you are seeking from the school (IEP eligibility eval, appeal of previous IEP eligibility eval, or 504 update), and give you advice on how to make the request.
2) The 504 coordinator (typically) is not a diagnostician, so he/she is not going to be the person who can best answer a question about things like how do you test for motor planning. You can learn a bit about what motor planning is by googling dyspraxia (developmental coordination disorder). There may be other disorders that are impacted by motor planning too, I just mentioned DCD because it is a diagnosis specifically surrounding motor planning, so info on it includes info on motor planning. You might also try just googling motor planning. Does your ds need further testing for motor planning? I would wait and see what the neuropsych recommends. My dyspraxic ds was diagnosed by his neuropsych. He had further OT testing, but the OT testing was primarily to determine that his issue was motor planning, not actual motor ability/strength, hence his OT testing varied from average to above average. AEH explained tests that are typically administered to assess motor planning - in our case, our neuropsych eval included the Beery VMI and Ray Complex Figure test, and a follow-up eval with our OT included the BOT2. Depending on what the neuropsych saw when he/she evaluated your ds he/she may have included these additional tests (as well as others) and he/she will most likely make a referral to the appropriate additional therapists for evals as he/she feels necessary.
Gotta run and not quite finished - I'll be back
Best wishes,
polarbear
