Connie, we just did Jackson and Yellowstone this past July. Two things pop into mind when reading your question.
One, in Jackson, the only good park is The Virginian. The bathrooms can use some updating (considering the nightly price), but they're more than serviceable and it's otherwise an extremely well-run park on the edge of prime downtown where it's an easy walk to restaurants or the free shuttle buses.
Two, we allowed three days for Yellowstone but that really wasn't enough (we spent every day driving, looking, enjoying) and we added a few more once there. You just can't see it all in a day or even three. And we were staying in the Park the whole time, part dry-camping and part with full hookups at Fishing Bridge. We just mapquested it, and the distance from your Valley place to Fishing Bridge (near the East entrance you'll be coming in from) is 58 miles, meaning you have an hours drive each way just getting started. I can understand why the guy who manages the Valley place would sell it as a good base camp, but for me personally that's way too much covering the same ground over and over.