This trip is actually a men's retreat so all of the planning is done for us by the leaders of the retreat. We just sign up, pay a fee, and go. Although for every mountain we have done so far the trail has just been a public trail with parking at the trail head. I would think it would be pretty easy to just pick a mountain/trail and go. A couple websites that I use to research the mountains when we figure out which ones we are climbing are
www.14ers.com (for 14ers only, obviously),
www.rockymountainhikingtrails.com, and
www.alltrails.com. The AllTrails website would probably be good for what you are looking for because under the Explore tab you can just zoom into an area on the map and it will tell you all about the trails in that area including comments from people that have hiked them before. The key to hiking these trails, especially the well known ones or any of the 14ers if you do end up deciding to do one, is to get an early start, like at or before sunrise. They get busy quickly and if you plan on going to a peak it is best to summit before noon and then get off the mountain because afternoon thunderstorms are pretty much a given in the summer and the top of a mountain is the last place you want to be when there is lightning in the area.