I currently have three under 18 months and I do not let them go on the climbers yet. I cannot safely watch them all while keeping an eye on the others. They play in the sand with sand toys etc until sometime after 18 months when I feel they are ready. It also depends on which park we go to because some parks are better for little ones than others. The one closest to us has lots of gaps so I don't let them up until the are older because it is too easy for them to get bumped off. I figure parents can let them climb when they ahve just one to watch and can go up with them. They learn the learn the rules pretty quickly and still have lots of fun