Well, the good thing about Dulles is that if you time it right, it's pretty painless. The interview process is quick and easy. We left here around 4 pm on a Saturday and were back by 7:45-8. All told we were at Dulles of around 40 minutes.

So you can also do the interview upon reentry at the airport. In terms of Richmond, they only do interviews on Thursdays from 8 am to Noon. There's only a couple appointments once a week, so they're comically difficult to get. I would say keep an eye on Dulles- I was able to get an appointment on a Saturday with short notice, which worked out great for us with our child.