Glamis- Loose sand, very dry, tends to get deeper off the "sand highway". Try Gecko road before you hit oldsmobile or competition hills, test out a couple of baby dunes. Yes, air down. Yes, get wider tires if you can. Stock rims and deuce, you can run dual 11.00's which is better than dual 9.00. might research if the tires you look at will fit the rims you have. Just a hint.
I'd avoid anything in the deep dunes. They can't get a truck to you that can pull you out. You're too heavy for anything out there to effectively get you out, until they bring the dozers in. You won't want to pay for that. Hills will be a challenge. Stay away from bowls. Take a couple of heavy nylon tow straps. If you don't need them for you, you'll have fun rescuing the stuck trucks and trailers.
For those of you who haven't been there, think sahara like dunes. No packed sand like pismo, or oregon, or idaho. Medium to strong winds at times, and amazing heat during summer. Or think Tatooine. They filmed it there.