prefer to get there..but open to ideas
In my opinion, if leaving from Tampa or St. Petersburg on day 1 sail to the "bulkhead" near Anna Maria Island; enter the ICW and spend the night at Moore's anchorage at Longboat Key just off the ICW. Next day, back-track a little, enter the Gulf via Longboat Pass and sail straight to Marco Island if you don't wish to make any other overnight stops. If leaving from Gulfport enter Tampa Bay via the Maximo or Skyway Channel, then go to the "bulkhead" and do the same as above. Next day, or the day after (depending on how long it takes to pick up your friends), sail to Key West. If leaving Gulfport and you do not wish to anchor overnight the first night, then blow out North Channel and sail directly to Marco Island. However, I'm sure you must know that the prevailing wind along the coast of SW Florida in summer until even mid-autumn is SE, your direction of outbound travel; unless there is a cold front pushing through, where-up-on the wind will veer SW-NW-NE before returning to SE. So, you might get a good two or three-day window to reach toward SE in October, but it can be pretty SLOPPY out there in the GOM until the wind clocks to NE.