Small local farm and playground
I have to agree with a previous reviewer that this farm is a terrific local destination, but not necessarily someplace that a tourist to the DC area would want to visit. Due to its location, it could perhaps be combined with a visit to the Steven F. Udvar-Hazy Center near Dulles Int'l Airport (the annex to the main Air & Space Museum in Washington, DC).
Anyway, the farm has ample free parking, a cute playground, and a small gift shop. The main attraction is getting to see the animals, especially the baby animals that are born there on a regular basis. You will see cows, horses, chickens, peacocks, goats, pigs, etc. Sometimes you will be there at just the right time to see a cow get milked (it is an actually working farm).
Kids can also take a hay ride (for a small fee) and pretend to drive some John Deere tractors. So come here for some basic fun, but don't expect too much.
I have been to this park several times for a picnic lunch with my kids and friends of theirs. Its a great venue to plan picnics for - the picnic tables on the grounds are usually empty and available, or you can throw a blanket down and sit on the ground. Spend a little time looking at the animals, playing on the playground, and then eat your lunch.
Another plus is on Wednesdays, they have a farmers' market, so you can eat your picnic lunch, and then pick up fruits and veggies for dinner!
Also, be sure to check their website - they frequently offer cultural events for the community.
Four stars for local residents; not a special trip to make for out-of-towners.
For local residents with young toddlers, this is the perfect trip to take between naps. The highlight of Frying Pan Farm Park is Kidwell Farm. The farm allows the kids to have a close-up view of your toddler's favorite farm animals - pigs, horses, cows, goats, sheep, chickens, bunnies - even a peacock and a turkey! On occasion you'll be able to see the new baby animals. Hayrides around the farm are offered on a pretty frequent schedule. Kids can even sit and play on three small tractors. The farm itself is pretty small - but that's why it's perfect for younger toddlers. There is also a playground, although probably more appropriate for older toddlers who can climb and go down a slide on their own. It's enough of a distraction if you need to get out of the house for a bit, but are not interested in a full day outing. There are a few picnic tables (not sure if reservations are required). Parking is ample and on the farm property itself.