+1 to the whole idea, even if I think that the Scavenger card is a bit too weak. Or, at least, I woudn't invest 3 turns for 250 crates only, not even hoping in the luck they'd be 250 Goldbars (too low chances of success, assuming the chances would be 1/8 for each resource).
I'd leave Goldbars out as they don't float like wood, but at the same time I'd increase the number of crates found.