Do you know which Airboat company will be providing your Everglades Tour?
Try emailing them with questions as to how they deal with pax with special needs.
I don't think a wheelchair could be put on board one of those boats, they don't have ramps as I remember, but I am sure they would be able to lift a passenger on board that needed special assistance.. They are easy to climb in and out of, the seating is on benches, quite basic.
It is fun, and scary at the same time!

Thanks for the reply emdia43, If the boats are easy to get on I could leave my wheelchair on the coach if it is not far to walk. I only need it for long distances. Can you remember roughly how long the boat rides are? The whole tour is 4½ hours which includes taking us to Miami airport. I like the sound of scary and fun!

We had about four hours to kill before a flight home.
We did the tour on the St John's River- http://www.airboatridesatmidway.com/ at the end of a cruise, on our way back to the Orlando airport ... we were there at the river for a couple of hours, the airboat ride lasted an hour if I remember right. AS you can see, the boats are shallow, easy to step into.
We had a short walk from the coach to the reception area, which was a combined tourist gift shop/cafe.
I haven't done the Fort Lauderdale one as we never had time before our flights home, but if I could I would do it.
WE saw LOTS of alligators and had a great time. I was scared but our boys said that was the best part of the whole vacation. You get close to them on the river banks and watch them slither into the river.....aaargh.

Thanks for the link, the pictures look great. I think the tour they are offering is at the Sawgrass recreation park. I know that the airboat ride is half an hour (maybe that will be long enough for me!). Unfortunately the tour starts at 8.30am and we don`t fly until after 8pm. There isn`t a lot of choice of what to do. I think this tour is our best option because they take us to the airport and our luggage stays on the bus while we do the tour. Thanks again for your help.

If you are trying to find something to fill up the day, before your flight why don't you go to Sawgrass Mills- a huge shopping Mall, about 15 mins from the FLL airport?

That sounds more like my sort of trip but, unfortunately, we our flying out of Miami airport and the tour bus which takes us to the Everglades will be taking us straight to the airport.