I believe that these events are designed for all ages, but primarily targeted at beginners and kids. Typically a 12 MPH average, it is not a rip, rail, and roost fest. It's meant to introduce people to the sport of enduro racing. Kids and adults run together. Typically a parent will ride 'X' class on the same row as their kid. The speed average is kept down so that you don't have 25 year olds on YZ-250s blasting past and running 6 year olds on XR-50s off the trail.
What's nice is that for at least two of them, there is a family enduro the first day, and a regular enduro the second day, i.e. Mini Moose -> Loose Moose, Pine Cone -> Jack Pine.
Big fun!