Suggestions - 2 hours at IAD or vicinity??
 

I will be at IAD tomorrow picking up family members - but there is an almost two-hour gap between when my parents' flight arrives and when my sister's flight arrives. I'd like to find someplace where we could sit and have a drink or a coffee or something while we wait for my sister, rather than just hanging around baggage claim. My general IAD strategy is getting in and out as quickly as possible so I am not sure of the answer to this - is there anywhere at the airport that is outside security and would fit the bill? Or, if we were to leave the airport, is there any place close by we could go, without driving all the way to Tysons or Reston?

I'm not sure if this is too much for a two-hour gap, but have you been to the Udvar-Hazy museum by Dulles? It's pretty cool - with a SR-71 Blackbird, Space Shuttle, etc. It's maybe 5 or 10 minutes from IAD.
Entrance is free, though there is a parking fee. Or you could just cab it.

IIRC the second exit off of the toll road has a starbucks about 1/2 mile south of the Toll Road. There is also the Fair Oaks Mall nearby.

you won't have enough time for the museum.

The simplest thing to do is to go to the airport marriott. I've done it occassionally when waiting. It ain't the cheapest or the best, but it is convenient and is in fact the ideal place to wait if the party you're waiting for has a cellphone. (it's not at the terminal, but damn close to it and has parking).

there are some other choices, but the rest force you to leave the airport and drive back.