People have brought kids up to age 8 or 9 in the past. I think age 5 would be perfect!
Just so you know, we have a lot of toddlers in the group so we often end up hiking at "toddler speed,"
(You know, walk a little, get distracted, ride in stroller, get out of stroller, hike a little, get distracted...)
Hope to see you on one of our hikes!
See you outside,
Beth