It's only 600 mi to Denver, so easy 1 day drive. Nothing to see in Eastern CO that you can't see in Kansas!
My advice would be skip the front range, spend 2 more hrs on 70 or 285 and drop the first night somewhere close to the Divide. Still summer and lots of Denverites clogging up the front range.
As far as backwoods great places to camp and fish, the entire western slope mountains is FULL of places to go.
I'm only really familiar with a small part of it, but Ouray area, San Juan Mtns are some of the most spectacular scenery and jeep trails in the country. Many can be run with a normal full size 4x4 truck. Definately a top destination to do some back country boondocking. It was a short trip with the gf s family that sealed the deal of me having to move there when I was his age. Went 4 wheelin all day every day!
Camping and fishing in the White River NF from just east of Vail all the way out to Grand Mesa is phenomenal.
Just have a CO topo map or gps maps w forest roads and go have a blast.
Couple quick fishing reccomendations that may be really hard to find (but I'm sure there's plenty more along the way, haha).
Mahan Lake, up Spring Creek outside of Kremmling. East side of Elliots Ridge.
Hike in couple miles from end of road down below the ridge. May have to ask locals where "spring creek" is in silver thorn or Kremmling.
Outside of Gypsum/Eagle up in the white River NF. Sherrif lake and the one next to it. Great fishing as well. Catch trout and stocked muskies (at 9000', weird, fish n game stocked tiger muskies in some of the lakes and tarns up there to kill the invasive species and save the trout). Hookjng a little Muskie on a 3 or 4 wt fly rod is a kick!
Blue River, out of Silverthorne. Gold medal catch n release stream but awesome fly fishing especially the northern areas behind private land halfway to Kremmling.
And the Eagle River, right in town, in Gypsum, great fishing for browns and rainbow. Try in the Willowstone Subdivision. (Lol, lived there, not many people fished that stretch through the subdivision).
So there's 4 of about 1000 good spots.
