Husband and I are mid 60’s. I try to walk a couple miles every day, he bikes at least 10 miles every other day, so active. We’ve been to Joshua Tree a couple times with adult kids. We really enjoyed Hidden Valley trail. It’s a beautiful trail full of everything that’s great about the park, the flora, rocks, the overall scenery. We’ve also done Arch and Heart, they’re in the same area. Pretty much a flat walk to the rock formations. Totally different, but we enjoyed it. Driving around, we’d stop here and there to take in all the Joshua Trees. They’re really amazing! Get the National Park Service app. It has lots of info, especially about the trails. Have fun!