A couple questions: 1. What are you hoping to accomplish by sending this letter? 2. Have you already said these things to him before? 3. Is he pressuring you for an answer right now or can you wait until you've done your research?
I don't think that this will necessarily hurt your DBing efforts. I would hope that he respect that you need time to figure things out. I think that if he's pressuring you for an answer on this, then you should send a simplified version of this email. Something like "I'm researching the options for how we can handle this best for the children. I will take your input for consideration and will incorporate it where I can. This is something that we both must agree on for the sake of the children." If he's not pressuring you, then I don't think that you should send anything right now until you've completed your research and have come up with a plan.
Just my $.02 B
Me: 29 W: 28 T: 10 M: 7 No kids 2 Dogs and 1 Cat With Parents: 09/16/07 Apartment: 10/13/07 Back Home: ~2/16/2008