Hello Anonymous. Not sure where your charter ends in Grenada. Moorings/Sunsail and Horizon are based in Port Louis Marina in the Lagoon. Customs is there in the marina so if you are sailing there on your last day and arriving in the marina then you will be at customs, as well. Other clearance options are:
Prickly Bay Marina in Prickly Bay (southeast shore)
Le Phare Bleu Marina (south shore)
Grenada Marine (south shore) mainly by appointment.
We have sailed down the windward side of Grenada and the fishing was great. Once you round the southeast coast you would then pass, Grenada Marine (anchor or mooring balls) then Le Phare Bleu (best to go into the marina or anchor in Clarkes Court Bay and dinghy over), then Prickly Bay before rounding Point Saline to head up the west coast to St. Georges.
The holding is sketchy outside of St. Georges but a good set is certainly possible and the dinghy ride in is not too bad.
BTW the clearance staff at Tyrell Bay are very nice and so are the officers in Grenada. One caveat, do not anchor in Mount Hartman Bay and hike to customs in Prickly. You will get your wrist slapped for that. The officers in Prickly Bay Marina want the boat in Prickly Bay, as well.
Good Luck. Kirk