To answer fully: You need a 4x4 vehicle with Low Range, not only a AWD vehicle. Low Range is a pre-requisite for this route and you will definitely need Low Range.
A Central Diff Lock "locks" your front and rear drive shaft when all four wheels provide traction. This is handy when either both front wheels or rear wheels has little or no grip, then, because your central diff lock is engaged, power is also still sent to the wheels that has traction and power not lost to the ones struggling with traction. The only reason you want your central diff to be dis-engaged is so that you do not get gearbox windup on tar roads.
Gearbox windup happens if your central diff is engaged and you are travelling on a hard surface that provides good traction, then, when you are turning, your front and rear wheels do not follow the same path; the front wheels obviously determines the direction and the rear wheels follow in the shortest path possible. Because of that, the front and rear wheels want to turn at different speeds to cover the same distance, but because your central diff is engaged, it is forced to turn at the same speed and the you get gearbox windup which is very bad for your transfer case.
In short, your central diff has no advantage in sand driving, neither is a rear or front diff-lock, those are actually never used in sand driving, using rear diff-locks in thick sand will want to push your car straight when you want to turn - not a good recipe for climbing a dune with a turn in it. Your car will under steer, you'll lose momentum and fail to clear the dune.
What you need for this trail, is a 4x4 with Low Range, and preferably one that does not have Traction Control or one where you can turn your tractions control off when in Four Wheel Drive and have engaged Low Range.
Traction Control and sand driving is not very good friends and are not ment to be used together. Traction Control is good to keep you on the tar roads when you are cornering too fast, not when you are trying to clear Big Bertha. When you are busy climbing a steep, sandy dune and you have the correct speed and momentum, wheel slip still occurs. If you have traction control on when this happens, power is cut from that wheel to stop it from spinning and sent to the other wheel which has good traction. This sudden "extra power" at the other wheel makes that wheel "grab" for more grip in the sand - which in lose sand makes that wheel spin, power cut from that wheel and more power is again sent back to the previous wheel - a vicious circle. Basically in the end all four wheels digs out chunks of the dune which results in a messed up, corrugated dune for the poor oke that follows you to climb.
I hope this answer is a bit more clear?