With Island in ~2' water.
Remove balloon wheels from cart, reach under and place cart in scupper holes, attach tires; flotation of tires will hold cart in place until you roll it up on to the shore.
If you want to make sure you don't lose the cart frame after removing tires (it will sink), attach enough pool noodles to the frame to give it enough independent floatation. This really helps cause the frame will then 'stay' up under the boat & in the scuppers while you attach wheels.
When launching. Put cart on first after unloading from car by tipping boat on side, load all gear, akas/amas, seat, you can even put in drive and bungee to up position. Roll to the water & reverse the above process.
I have pool noodle on the bottom bar and 2 small 1" pieces on the left & right of the top bar. The 1" pieces on top bar serve another purpose in matching the contour of the Island bottom to the cart - stops the dreaded dent in the hull.