AVOID AVOID AVOID on weekends. Midday during the week is great, though. The boardwalk through the reed marsh is bursting with bird life. the path gets pretty twisty towards the end at Mt Vernon but the hills are small (though steep in a couple of spots for a short distance), so take it easy if it is wet.
Mount Vernon is a great weekend ride, though the trail is heavily used. Very scenic once you get past Belle Haven.