On getting stuck out there, the times I've been out on the beach it's pretty common as you drive along to see people stuck and digging out of the sand in all types of vehicles. I took my Jeep Wrangler out there once and left 35psi in the tires because I wasn't going to be doing the stuff other people do out there, and almost as soon as I got up into the dry sand I was stuck. Before I dug myself in too deep, I let some air out of all the tires and the Wrangler drove right out. So the air pressure is clearly important.
If I ever did take my glass DP out on the sand (I don't intend to) I would bring along some good strong large boards. If you get stuck you can dig out from under the jacks and put the boards under the jacks and use the jacks to raise the rear wheels out of the hole and then either fill in sand under the tires, or put boards under the tires.