Another option to consider is JetBlue, which offers tickets as low as $49 one-way from JFK to MCO. The very low fares tend to be for the less convenient flights, but for $69 or $79 you should be able to snag a more convenient time. The flights have always been pleasant enough, with a snack and a drink served, as well as 30 or so channels of live TV in every seat.

You may also want to consider flying to TPA (Tampa), which is west of Orlando. There's a lot of construction along I-4 from Tampa to Disney, and it is a bit of a longer drive than MCO, but probably closer than DAB. It also depends a bit on where you're staying I guess.

As for finding low rental rates, go to Orbitz and run a check there. If you don't have a US credit card, you can't book with Orbitz, but it's a great tool to compare rates. I usually end up renting with Alamo or National. If you rent from MCO, you can save some time by renting from one of the in-terminal agencies. When you go down to retrieve your bags, go down another level to the car rental counters to take care of the formalities while the rest of the family waits upstairs for the bags. At busy times this can save you even an hour.

As for the Disney and Universal passes, I've not kept up with those lately, but you should look around a bit on the web. If that fails, get a guidebook at your local bookstore, which often have many tips.

Enjoy your stay in central Florida! I always do, and coming back is getting harder every time...