There is no need for 4x4 in Arches or Canyonlands NP's. Moab is a great jeeping area outside of the parks. In Colorado, I have been up Pikes Peak by train and by highway (it was partially gravel when I went up). The train is my preference for Pikes Peak. You can get all of the mountain driving you need on Hwy 550 between Durango and Ouray (best or worst is between Silverton and Ouray). Animas Forks can be done in almost any 2-wheel drive vehicle but moderate clearance (think pickup truck) is probably best. I have seen mini-vans there, but that is not probably for someone that has never driven on gravel/rocky roads.