OK guys, you've not let me down on the advice front yet (would love to be able to return the favour sometime!). Potential Itinery (departing KC on Sun 5th December)
Day 1 - Drive from KC to Denver (stay overnight in Denver)
Day 2 - Drive from Denver to Green River, just north of Canyonlands NP Utah (stay overnight in Green River)
Day 3 - Look around Canyonlands NP (stay overnight in Moab)
Day 4 - Look around Arches NP (Stay overnight in Moab)
Day 5 - Look around Mesa Verde and 4 Corners NP (Stay overnight in Bluff)
Day 6 - Look around Natural Bridges and Monument Valley (Stay overnight in Flagstaff)
Day 7 - Drive to Las Vegas.
I reckon it's doable and not too strenuous (at least streets and trips seems to think so!). Thanks for all the advice on I-70 and the weather. Any issues with regards to this itinerary? And of course any suggestions as to things I might have missed in the area worthwhile visiting, or things I'm doing that aren't worth it?