I have been into Onancock. It is along trip through the channel and I remember there being around 50 markers or so. It is a beautiful place to visit and crossing the bay from west to east usually lends itself to nice winds.
When I went to Onancock, I left out of the Coan River. I skirted Tangier Island, and then sailed into the Channel.
If you leave Quantico, you could probably make it a nice sail to get to Canoe Neck Creek or Bretton Bay.
Bretton Bay is a beautiful anchorage. There is a horseshoe shaped area with 10 feet of water on the mainland Maryland side of Bretton Bay. It has high banks that create shade earlier in the day than most other places. You will tend to see eagles and osprey there.
If you feel like going into a town you can go all the way back to the area around the last marker near Leonardtown and dingy into Leonardtown. Don't go too far past that last marker to anchor as it gets shallow. There is a town dock there that you can tie the dingy up to but don't try to get your boat back there.
On the second day you can make a short day to the Yeocomico and anchor near Kinsale Marina. There is a nice restaurant there and you can anchor in the first cove past that marina. There is a nice area to swim on the next point past the anchorage.
If you don't want to go to the Yeocomico you can go into the Coan River. There is an anchorage in the first cove past the campground. There are a lot of oyster steaks in the channel back into the cove but you can go right by them.
The next day it is a nice sail over to Onancock.
