I've run two different community (or district) choirs. My experience has been to get the Pastors of the churches buy in first. Normally, most pastor see the need for everyone to "come together" as one unit. After all, when we get to heaven I don't think there will be the Missionary Baptist Section, and the COGIC section.
After the Pastors were on board, they helped me get their Minister of Music and Choir Presidents on board. This was the real key because I attended some of their choir rehearsals and they helped get their choirs involved. I picked up some musicians from this, scheduled first meeting, and let God move!
God will provide for you. I ran one in KCMO for about 4 years and it was a lot of fun and a blessing for the most part.
Good Luck.