The foot rest is 18" from the bottom of the stilt on Powerisers. This can
not be adjusted.
Nettie,
here is a link to a fellow clown that makes adjustable stilts - which are good for beginners. A possibilty for your grandson; or at the very least - a concept if you try to build your own.
Frog Leg stilts are similar.
These are the next set of pegs I want.
(in french - they have an english language website - but I couldnt get it to come up on my laptop today)