OK, I need a sanity check...we are headed to WDW in 44 days

and I'm trying to figure out the best way to get 3 carseats down there. Here are the facts:
- We are flying down with a 3 year-old and 1 year-old twins. We didn't get airline seats for the twins and I don't know the rules for the 3 year-old (can I just use her regular seat in the airplane?)
She is not required to use a carseat, but if she weighs less than 40 lbs., it is recommended. If you take it on board to use, it must be positioned at the window and NOT in the rows immediately in front of or behind the exit row.
Also, just FYI, you two adults may NOT sit in the same row. (Well, you can, but only if you are across the aisle from one another.) Because there is only one extra oxygen mask per row section, there is a limit of one lap baby per row section.
- We have to have the carseats the first day we are there, we're taking ME to the resort then renting a car at the car care center to drive to my uncle's for dinner that night.
- I will not rent any carseats.
So here's my question...could I ship the carseats to the resort? If I did that would it cost us an arm and a leg and would I be able to get them as soon as we checked in?
Unless money is really no object, you could realistically do it only do it if you would not be using the carseats for several days before leaving for WDW. I checked FedEx from my area in the midwest, and it is not cheap, because the boxes would be over-sized. Assuming that they are lightweight seats (Scenera or similar, which weigh 10 lbs. each), overnighting two carseats to Orlando should probably cost about $550.00. Sending them regular FedEx ground would be significantly cheaper, but still about $125.00. (Those rates are one-way, BTW.)
Or should I suck it up and try to gate check the carseats which means toting them through the airport along with 3 small children and all our carry-ons? Any help is greatly appreciated.
Normally I do NOT recommend checking carseats with baggage, but in your case I might make an exception. If you can strap them up into a bundle and heavily pad them with beach towels or the like, it might make sense to check them. (I'm not sure that they will accept them for no charge if they are boxed, unless they are in the original boxes. Boxed carseats will exceed the oversize baggage limit, so if they are not identifiable at a glance as carseats, you could be charged up to $100 each to check them.)
Otherwise, I would say that if you don't already have them, you should invest in a few items to make it easier to get through the airport.
1. Three sets of walking reins for the kids. The strollers will have to go through security without the children, and with that much baggage to corral, having them on harnesses will be immensely safer and less nerve-wracking. Note that if they are wearing them through the scan-gate, they may not have any metal parts and they may NOT be the kind that has a stuffed animal/backpack on them.
2. Spare padded socks that you don't mind tossing, unless you are comfortable with having them all barefoot it through the airport. Take the kids shoes (and your own) off and put them in a carryon before you even enter the security area. Go through in sock feet, and don't stop to put your shoes back on until you are FULLY away from security and can sit them down away from the chaos. Also, fully empty your persons of everything except your ID's at the same time you take off your shoes. Put it all securely inside your carryons before you even approach security. If your older child cannot manage a REAL rolling carryon bag (not a tiny bag), then don't give her her own bag.
3, A sling or carrier for one at least one of the younger children. You should use this while going down the jetway. One parent is going to have to be responsible for carrying the carseats down the jetway and folding the stroller, so the other parent must be able to keep a hand on all three kids while that happens. Having at least one of them in a carrier will help make that easier. (Besides, it will come in handy at WDW in the ride lines.) NOTE that you CANNOT use the carrier to hold your child on your lap during takeoff and landing, so remove it as soon as you enter the plane.
4. Carseat satchels. Under the circumstances it is probably best if you use the backpack type. Put your smaller carryons INSIDE them with the carseats until you reach the gate. You should be able to get by with two if you nest two seats inside one. I recommend the Prince Lionheart bag, it is HUGE.
Alternatively, you can plan to carry the younger children AND your carryon bags, have the older child walk on a rein, and use your double stroller to move the carseats, in which case you'll need a couple of short bungee cords to secure them. Get the kind with PLASTIC hooks; TSA has been known to question metal-hooked bungees as possible weapons.
5. Do not attempt to take rollaboard carryons this trip, unless you can limit yourselves to one that holds everything. One person will need both hands to move the stroller through the airport, so the other will need one free hand to corral the older child and deal with the carryons; one person can carry more than he can pull. I think you should stick to soft bags that you can put in with the carseats or on the handles of the stroller.
Also, be sure that you have plenty of $1 bills with you, and USE the Skycap services when you can; it will help immensely, though at most airports they are not allowed to work airside, so from Security forward, you will probably be on your own.
Good luck!