I'm not sure. It's a park, and it's not like anyone is guarding the parking lot.

I found this on the park's website. The National Park Service recommends going to the "Planning Your Trip" section of a park's website to find out about accessibility: The Washington's Headquarters Museum and the Jockey Hollow Visitor Center are fully accessible to wheelchair users Partially accessible bathrooms are located in the Washington's Headquarters Museum and the Jockey Hollow Visitor Center (stalls are wide enough, but doors into the bathrooms are not automatic). The following walkways are paved: from the visitor parking lot into the Washington's Headquarters Museum and from the visitor parking lot into the Jockey Hollow Visitor Center. The Jockey Hollow section of the park has more than 3 miles of paved roads open for touring by private vehicle. Wayside exhibit panels along the route are partially accessible, on paths and in flat, grass covered areas.

Yes, you can have dogs on a leash and there are receptacles available. The leash must not be in excess of 6' in length. It's a lovely area - have fun!