I prefer to book directly through Disney. The prices are the same, and I can access my reservation myself, without having to wait around for a
travel agent to get around to it.
If you go with a TA, I would recommend NOT using a
AAA travel agent. I have had bad experiences with them, and if you do a search here on Dis, I am sure you will come across a lot of posts about AAA agents who have been less than great, esp. when it comes to Disney,
As for codes, you can check ww.mousesavers.com They have all the discounts as they come out, and if you book yourself, you can call and have the code applied to your reservation. Too, your agent can too, but that's a call to the TA for them to call Disney, when you can call Disney yourself -- a call is a call, lol