Grand Canyon or Yellowstone for 2015?

I am in the begining stages of planning our 2015 vacation and I would like some opinions on where to go. I have narrowed it down to either the Grand Canyon or Yellowstone. I have been to both places as a kid but the rest of my family has never been to either place. We are a family of 2 adults and 3 kids ages 2 1/2, 12 & 18. We are experienced tent campers and hikers although now with our little one we won't be doing much hiking at all. We are located between Houston and Austin, TX and we have 2 weeks total for this trip.

Option 1 - Southwest trip: Palo Duro Canyon, stops along old Route 66 (I just gotta stay in a Wigwam), Painted Desert/Petrified Forest, Grand Canyon (how much time here?), then down to Tombstone (my husband loves old west history), finally over to Carlsbad Caverns before heading home.

Option 2 - Yellowstone/Tetons: Would need 2 nights on the road to get there and get home. Should I also do a night in either Jackson or Cody before entering? And which park first? How long in each park? Four in Yellowstone and three in Tetons? Or Five in Yellowstone and two in Tetons? I have already decided on Canyon for camping in Yellowstone due to it's central location and showers and either Gros Ventre or Colter Bay in Tetons.

So based on all that I would love to hear you thoughts and suggestions.