You might look at a cadet chassis or maybe a 28mm frame, but more important is looking around and see how people in your area are set up. The karters are a pretty good bunch to get info out of and that will save you lots of time.  Where are you located?  You are more than welcome to come see my daughter’s(10y/o) set-up.

Been to Comet yet?  Just east of Indy on 40, just outside Greenfield.  Been at it forever, great group, karts, motors, parts, help and advice.  Anyone there knows karts front to back.  Can probably look at the grandkids and tell you what size you need.  They all have won about a billion kart races, and helped just as many.