South Seas Resort is a good stay on Captiva for a night or more. The ammenities ie pools, restaurants, etc are on the resort level definitely a place to chill or if you play golf they have a course. A little walk outside the resort gated is Captiva's downtown where there are excellent restaurants like R.C. Otters, Captiva Cantina, Key Lime Bistro, Mucky Duck... i could go on...
I recommend a must stop for the night is Cabbage Key. Which is approx 20 mins north from Sanibel (the way i cruise lol). Jeff is the dockmaster. They serve breakfast lunch and dinner. It is an island to get away and just relax. It was said this island helped inspire Jimmy Buffet's "Cheeseburger in Paradise". He has a plaque on the wall but they have no fryer on the island so some of the lines don't match... If i had to pick one place to go this is the spot. Get server Debbie if she is working, she's a hoot! Tell her Tom from Jersey says Hi. (She prob will have a brain fart but she may remember since i was there last month). Got to have a Cabbage Creeper if you partake in cold refreshing adult beverages if ya like it without the alcohol get a Cabbage Crawler!
Cayo Costa State Park has a docking area where you can tie up and hitch a ride on the tractor pulled wagon to spend some time at the beach. You can also drop the hook in that area there's a nice mooring area which is really safe and seems like the spot you will see some moor overnight at.
Further north you have Boca Grande. There are several marinas where you can dock overnight and get to visit a neat high end island. We actually rented a condo there and that's where we stayed for the week. Cool history in the downtown with neat restaurants. You could look up Mark Futch and go for a seaplane ride.
North of that you can go into Gasparilla Marina which is a great marina. Really well maintained with whatever you need. They have a restaurant on site also. They have good fuel prices with non ethanol fuel too.
Lemon Bay area gets a little skinny for the IPS boats.
Things to look for also. Cape Harbour Marina is amazing. Rum Runners is there and a bunch of other restaurants shops and bars. The Westin is in the same area and is worth a look. They are both at the mouth of the Caloosahatchee.
Key West is only 3-4 hrs from Ft. Myers!
How long are you in the area? Also you boated from the OBX? Which route did you take?