...I'm going to Disneyland

Well, actually we're going to disney world, but that isn't quite as catchy. We decided that it was time to take the kids to Disney. Part of me wanted to wait another year, but the other half off me knows the kids will have a great time, even if they are a little young to do everything.
Originally we were going to drive to Florida to save money. We were really surprised at how awesome the kids did the weekend we did all that driving to pick up the camper, so we figured they would be just fine on the ride to Florida. My plan was to rent a bigger suv of some kind so we'd be a little more comfortable, but once I started researching a car for the week, plus a couple extra days for drive times, I thought maybe I could find a decent airfare in the same range. I found an awesome deal on travelocity for our flight. It was $170 a person round trip, non-stop. Then I found a package deal for the airfare plus 6 nights in a two bed/two bath condo for only $100 more. So we are flying 5 people (Megan is still free thankfully), and staying for 6 nights for under $1200 after taxes and fees and all that crap. We are still thinking about renting a car while we're there, but we obviously won't need anything really big or nice since we'll just be traveling around town, and possibly driving to Sean's mom's, which still isn't far.
Thanks to the company Sean works for we get free tickets to Sea World, and they are building a water park that should be open by the time we go that we also get free tickets too. That will save us a lot of money because tickets to go anywhere down there are crazy expensive. If anyone has any good discount sites or places to go for deals on tickets, please let me know. I'd also appreciate any tips on flying with the kids. Not just how to keep them entertained on the plane, but getting through the airport with all our crap successfully. 5 people traveling for a week long vacation equals a lot of stuff. Ideally we'll check everything we can, and Emma and Nathan can each carry at least their own backpacks with their coloring books and small toys and things like that in them. I'm tempted to buy them each a little rolling suitcase to pack their stuff in so they can pull that, and then Sean and I would only need one bigger suitcase for us and Megan. Another thing we need to think about is Megan's car seat. She's flying as a lap child, but we'll need her seat for the rental car in Florida. Has anyone ever rented a car seat? Are they safe? Are we better off bringing her carseat and checking it? Obviously I have lot to figure out, but we still have a couple of months to plan everything.
We haven't told the kids yet. I am trying to get through the holidays and then I'll probably spring this on them. They can only handle so much excitement at once, and once I tell them they will probaly ask everyday how many more days until we leave. I don't need to hear that for the next 3 months!
If anyone wants to join us we'll be going at the beginning of March. We will be leaving on a wednesday and returning on a tuesday, which is how I got such a good deal on airfare. I can't wait!