DR Jane - Yes, there is nothing around Dulles Airport. IAD is it's own kingdom so to speak. Alas, most of Northern Virginia is not pedestrian-friendly, unless you count malls and "Towne Centers". So, you could always stay at Dulles Towne Center or Reston Towne Center. You'd have a nice choice of hotels, and some decent shopping. However, as for nature and scenery, not so much.
As for a taxi to IAD... The cheapest alternative - depending upon where you end up staying - is take to take the free shuttle bus from the West Falls Church Metro Station. So, if you happen to stay in DC, you could always just take the Orange Line out to West Falls Church and go from there to IAD.
When I have a bit more time to think about, I'll post more.