I think your concern is justified. Without knowing the clearance between the bottom of the cart and the ground I am not sure if this suggestion will work.

Purchase a couple of hydraulic jacks, small ones and bolt the base to the bottom of the cart - the jack would be upside down compared to how you would normally use it (the base would normally be on the ground. Then to level the cart you would crank the jacks so that the jack head pushed against the ground leveling the cart.

If you don't have enough clearance for a jack you could consider mounting appliance levellers to the bottom of the cart.