One of the classic designs for the purpose is the Optimist pram. There is a national Optimist class association that offers plans for homebuilders in wood or wood/epoxy at $48, and may let you build all the boats you want from one set; they do have specific interest in developing the class. Check them out at optiworld.org.
The design was originally developed, if memory serves, after WWII for construction out of a single 4x8 sheet of plywood (one of the miracle materials of the war).

: Any suggestions to source a free design for a first time build for kids with
: sailing capability for use on an inland lake?