Albino what ever design you end up with, a big improvement is to run Go-Kart wheels on it. Reason being they dont give hassels running on soft sand.
Rims is the only item you need to buy, the tyres you can get from any Karter at a race day. As soon as the tyres go off (rubber looses grip) they toss them out. So if any mates have Karts or you are handy to a race track, these are by far the better option.
I know from experience here in WA at race meetings, moving Karts across soft on kart trolly in sandy area's. Thin profile

wide profile

Mineral