I don't know how much reptile-related things are at this event, but the Mid-Atlantic Turtle and Tortoise Society will have a table on Friday and Saturday.

http://www.superpetexpo.com/shows/chantilly/

Friday, April 1, 2005
Kids Admitted FREE! 4 PM - 9 PM

Saturday, April 2, 2005 10 AM - 8 PM
Sunday, April 3, 2005 10 AM - 5 PM

Admission
Adults: $10
Kids 12 & Under: $5
Kids 3 & Under: FREE

Katrina