This 5 year old with Polio is a bit small for even the small cart, but should grow into it. Mobility Worldwide West Michigan Affiliate has developed an add-on kit so that a small cart can be transformed into a push-pull cart (and back to crank cart) by changing out the crank assembly.
https://www.youtube.com/watch?v=CDeACjyplTQ&rel=0&modestbranding=1
https://www.youtube.com/watch?v=_DbcBa1zn_w&rel=0&modestbranding=1