On holidays my two, boy 10 and girl 13, will happily do 2 to 3 hour rides around forestry tracks and similar terrain. Say 10 miles tops?
At home the daughter has now discovered horses so is rarely seen at weekends, while my lad will still go out for similar rides if he’s at a loose end. But mainly he’s playing cricket/footy etc. So that ride may be once a month or so.
But, if you go at a steady pace with a few snacks or picnic, they can do quite a lot.