1. don't take the dogs.....at least not on your first trip.
you got family going, too. put the critters in the station wagon.
(hehe, or on the roof romney-style!)

2. plan your route. colorado has hills. the interstate cuts through the mountains
with tunnels and bridges. 100 miles flat/direct could be 140 with lotsa climbing.
you might even consider driving your route (and an alternate) in the car beforehand
to know what to expect.

3. plan on round trip, but be aware that you may be too tired or sore to ride back.