Good question. I'm from Ohio so I don't hear much about the shoots in the deep south. But, if you go to the 3Rivers web site, they list 3D shoots for the year, or at least the ones they know about. Just pull up their web site, and along the top you will find a link to "Neat Stuff." Then there is a link to 3D shoots, by state and date. I just looked for MS and didn't see anything listed for 2007.
Not sure how big you want to go with this, but it takes a lot of work. Sounds like you have the location and at least some of the lodging handled. Some may also want to stay in a motel if you are planning a really big gig. Then it is always nice to have vendors there, food, and a bunch of people to help. Everything from parking to registration, to range set-up, advertisement, etc. You are not starting too soon for 2008, if this is to be big.
But back to your question of the date. I am not familiar with any big shoots (Cloverdale, Denton Hill, ATAR, Compton) that would be a problem for you since you are so far from them. Might check with all the archery clubs you know of to see if they have dates for other clubs having shoots.
Good luck!
Goose