We rented an RV and traveled from Denver to Yellowstone and back because we knew we would have trouble finding sleeping accommodations for six people.
This is the only way to travel with two parents, three children and a mother-in-law. The RV rented for about $1000 but that was a very reasonable price compared to the price it would have cost to stay at hotels for 10 days. Plus, we saved a lot of money on food because we prepared, served, and ate our food in the RV Kitchen.
The RV was perfect because it was a rolling house with a kitchen, beds, and bathroom. The kids enjoyed being able to travel without being strapped in and were easily entertained.
It was great being able to fix a meal while going down the road, not having to stop because of bathroom breaks, and when we got tired, we could rest in our beds--even take a nap in the middle of the day.