Where are you flying from? There may be people who can give you a good idea of what a "good" fare is.
We went last 12/13-12/22. We fly out of BDL (Hartford) I did not buy when fares were first released because I wasn't sure we'd be able to go.
Ultimately, I finally "first' purchased our tickets on SWA on 10/19 for about $240 RT which was a fare I could live with, but not as low as I would have liked. Between 10/19 and 11/20, I rebooked 4 times and by the time we flew, I paid $155 RT (which is lower than I've paid in a couple years!)
(I also had some date flexibility that I factored in)
I would suggest you get some guidance on what is a "good" fare (could also read that as "Likely") for your specific departure airport and dates.
If SW flies from your city, I would book SWA when you see that fare, just because you can get full credit if the fare goes down. Of course, this assumes that you'll be able to use the credit within a year of the original booking date.
If you don't think you'll be flying again, then buy when you see something you can live with. For our December trip above, I will admit that I was getting pretty nervous in October that we might have to cancel the trip because I had waited too long. When I booked 10/19, I got fares that were lower than they had been in September.
I believe it's up to 1 year from the date of original booking. So, if they booked their airfare in March 2013, and the fares went down in August 2013, they would have until March of 2014 to use their credits...
This is correct, but important to note that they would have until March 2014 to complete a trip - not just purchase a new ticket.
As far as visiting Kennedy, etc. I would plan to rent a car. Start checking dates now and again, if you find something reasonable, book it. Car rentals are easy because you can cancel and rebook as much as you want.
Check rentals from/to MCO for your entire trip - or check for two days rentals at one of the locations on or near Disney. I seem to have alot of luck with Dollar at the Wyndham Lake Buena Vista Resort (which is right across the street from the DTD bus stop. I take a bus from the resort to DTD, Walk across and get my car, and frequently return the car to MCO when we fly out
Good luck!