Don't you work with the Sea Scouts, or some sort of scouting organization? Why not build a dolly as a project for the kids? Tag has a good PVC design, while my old wooden dolly with steel axle was a bit clunkier but it still fit into the trunk of 'The Mighty Camry.'
You can buy everything you need to make a dolly down at the nearest Home Depot, including pneumatic tires for wheelbarrows or handcarts. Steel rods and hardware come in a range of sizes & prices. You make the call on PVC vs. wood. Cheers!!!
I'm sure Tag will share his PVC dolly design, it's pretty clean and probably weighs less than my old wooden number, I just had plenty of free and perfectly good scrap lumber available from job sites in Coronado... looking back, it's incredible how much wood was wasted in those days when construction was booming.
No lie, a handy person could've built a tiny home from all those scraps... or maybe one not so tiny. Whenever I went camping, I always hit up construction sites for firewood... it's no big deal as long as you ask first, no need to trespass on any site, those hands were usually glad to see the wood get hauled away.
I used to know half the guys who worked in those construction crews... many of 'em friends or acquaintances of mine. I'd show up with boots & gloves, ask 'em for some scrap lumber, and scientifically fill the trunk of the Olds back in the day. Car would look like a low rider pulling the grade up into the mountains, LOL.
I also worked for one or two of those outfits, but even after those days passed I would always get my scrap lumber from job sites, no point in buying wood when there are clean lumber scraps available for free, aye? Just gotta watch for nails and whatnot as you select the pieces you want...
I do not like the Win Design dollies. Their plastic gunwale supports seem to be cheap and they leave awful red marks on the sides of the boat. They also ride low enough that when I'm pulling the dolly it is very easy to tip the transom of the boat into the ground due to their low ground clearance. The plastic wheels are nice because they do not go flat, however, I do not think they would work well at all on a sandy beach.