My husband, 6-year old, and I made it up to the top of Wind Cave, no problem. Jen H.'s review was right on...it took us an hour and 35 minutes to go up, 40 minutes to get down. We went sloooooow on the way up and took several water breaks. It worked our muscles, but I wouldn't call it strenuous, at least not at the pace we went at. With great views all along the way, we all enjoyed it very much.
$6 per carload fee applies to enter Usery Park.