A few questions.
1. Will access happen outside and inside?(I assume so based on the 300 acre statement.)
2. Are you looking to provide 802.11b/g only, or will you also want to provide “a” and “n” as well?
3. Is this a mesh solution you are looking to deploy? Or just simply placing AP’s with wired connections back to one or more switches/chassis’?
If you are wanting to do what I think you are, there are several different vendors that come to mind. SonicWall is not one of them. They have very good products for the SMB market, but they don’t really get a lot of play in the Enterprise area. Cisco has some mesh AP’s and can work fairly well in the environment you have somewhat described. I would also look at Aruba, and Ruckus.