There are hayride and big giant slides at the Burke Nursery's Pumpkin Patch and Playground. We went there last year. It was a bit pricey on the weekends, I think it's $12 a person! They have a website.
Cox Farms is having its Fall Festival until the 7th, 10AM-6PM daily, admission $9/person over age 2 weekdays $15/person over age 2 weekends. They have hayrides, animals, pumpkins, corn mazes, hay slides, rope swings, hay tunnels... It's a blast, we're planning on going sometime this week.
Oh, Cox Farms is in Centreville, VA. Here is the website: