no 'sessions' as such, but there will be lots of impromteau music all day in the picnic grounds of Glen Echo...(Right in the middle of the activities...this is not a big park)
Friday night there will be an 'open sing' in the same general part of the Maryland area...if you are around then.

Get there as early as possible, as late arrivals will need to park at a more distant lot and ride a (free) bus.....this is really easy to do...all marked and clear.

Look forward to seeing you!