Right on!!!
My 6 yo graduated to a trailing bike when he was 4-1/2. We can now hit almost any singletrack or fire road that is not too technical (Gold Camp Road, Cheyenne Mountain State Park, Monument Preserve, Greenland Open Space, Salida Mountain Trails, Midland Trail in BV etc.). Great training hauling the kiddo around, as well as fun to get out and enjoy nature.