I have been houseboating out of Hall's Crossing for the last 7 years. However, prior to that, I used to remote camp with friends in Crosby Canyon at the back of Warm Creek Bay. I don't know how it is now with a lower water level, but back in the 90's it was always a good place to camp, and the only crowds we ever saw were on the weekends.....it was very nice during the week. It worked well for us as it usually took us at least 3 boat trips to get everyone and everything out to our camping spot. If you can haul everything in one load, then going uplake sounds like a good idea.
I don't know how long you will be camping, but if you are going to be out for a week, a chunk of dry ice wrapped in newspaper in a cooler will last much longer than ice blocks to keep your food and drinks cold. Also, freeze all of your bottled water, etc. to aid in keeping your coolers cold.
Also, if you are camping along the beach at Powell, you are required to have a port-a-potty. The rangers do come by the campsites and check, and will cite you if you don't have one.