When I was 7 my Dad took me camping for the first time, made me carry my own backpack with sleeping bag and supplies, about half way up I asked if he could carry the pillow I brought as I had been overzealous about what I "needed" so he took that but made me hike with the pack. We made it, it was probably 2 miles up, I've been there since as an adult it took me 1 hour but as a kid it felt like all day. Point is, even young kids can do it they just have to be taught early to carry their own weight then they can come with you so, just 2-3 more years and you're golden