This picnic is being hosted by the DC Region Atheists and they have invited everyone from the various participating groups in the Washington DC Area Coalition of Reason to join them. They hosted a similar picnic at this site last year and about 60 people came, including a number of children.
The site is a very family friendly picnic site. There will be very little traffic on Beach Drive since much access to the road is shut down for the weekend. For humanists this is World Humanist Day.