Hi Sam,
Good luck with the wood! We also have to pull our Hi-Lo over lawn (about 25') to get it onto our driveway. We had the same original thoughts as you, to somehow preserve the planking for a future alternate use. Well, its never happened... the first batch of wood was a better grade of 5/8" plywood, ripped by HD into 2' X 8' runners (which we laid end-to-end in the wheel tracks). The very first time (with our 19 footer) we used them, listening to the wood fibers split and crack under the weight, I knew they would only ever be used as planking. We started out using two tarps laid end-to-end over the planks, only to discover that turning the truck wheels on the tarp twisted the tarp badly. Even storing the plywood vertically and protected from weather, we only got about four years out of them. Currently on our second set, I bought not expecting the planking to be for any other use, and spent less by getting 1/2" chip board sub-flooring, again letting HD rip it into 2' X 8' planks. We're through one season with this stuff, and so far it seems to be holding up as well as the plywood. Just lighter to carry and a bit easier to place, lift, and store. I just put it right on the grass, its never down long enough to pick up very much moisture. Even without a tarp, I minimize steering wheel turns because the tire tends to grab and turn the plank with it.
If I can ever find (for a cheap price) a few lengths of steel surplus SeaBee runway matting... that would be the perfect material to use as drive-over planking!
Take care,
Jim