That looks very good!
For reference, I'm using these in both 22mm and 30mm wide versions on my fire truck, with the included foams and Tamiya 1/14 truck rims. They have no problem carrying about 12 pounds on 6 wheels, but I don't know how they would handle beach sand. They're 85mm in outer diameter.
https://www.stellamodels.com.hk/trac...u-pr-8495.html