If you decide not to use a carseat or a CARES harness (for your sanity I don't recommend this, but you have the right to forego it), understand that the FA's will most likely require you to hold her during takeoff and landing, and at any time that the FASTEN SEATBELT signs are illuminated. In the event of turbulence, a lap belt will not safely secure a child who weighs less than 40 lbs.
The PP is correct that if you do use a carseat or CARES harness, you will be required to place it in the window position, because Federal law requires that it not impede emergency egress from the row, not even if the person being impeded is the child's parent. (Also note that it cannot be placed in the rows directly in front of, or directly behind, the exit row.)
Here is the entire FAA circular on the subject
https://www.faa.gov/documentlibrary/media/advisory_circular/ac_120-87c.pdf
(Note that the FAA "approval sticker" does not actually mention the FAA. What it says (in RED lettering) is:
This Restraint is Certified for Use in Motor Vehicles and Aircraft.
Also, a couple of specific things about SWA:
1) If your DH commonly gets seated in the exit row in order to get that extra legroom, be aware that he cannot sit there if an FA knows that he is part of your party. I'm sure that you already knew that your DD can't sit there, but SWA is, AFAIK, the only airline that enforces the FAA recommendation that you cannot sit there if you are traveling with a child, even if the child sits in another row. (This is because people seated in the exit row must agree to help in the event of an emergency evacuation, but airlines know from experience that parents are likely to abandon that role to take care of a child. An evacuation is very unlikely, of course, but the FAs still have to enforce the rule.)
2) If you are not installing a restraint, you should approach the gate agent and ask for a reserved card for your child's paid-for seat. Doing this will save you some hassle during boarding, because the FA's are trained to assume that a baby just sitting in a seat without a carseat is probably a free lap child, and that you are attempting to hold the seat open for her without paying for it. (Which is fine if the flight isn't full, but almost every flight to/from MCO these days IS full.) They will ask to see her boarding pass before they will believe that it's a paid seat. Getting a "RESERVED" card from the gate agent will make it completely clear that the seat is paid for, and you won't be bothered. (The FA will collect the card from you after all passengers are seated and the boarding door is closed.)
FWIW, there are backpack satchels that make it a lot easier to carry a carseat through an airport (and that protect the seat later when it is checked, after your child is big enough to get no benefit on the plane but still needs it at your destination.) You can also transport a seat by putting it into your stroller or upside down over a rolling bag and securing it with a couple of plastic-ended bungee cords. (Never check a stroller with your luggage; always gate-check it so that it will not get bent by ending up at the bottom of the baggage hold under thousands of pounds of suitcases.)
Here is a brilliant travel tip we swore by when our kids were that age: the "counting hands rule". This "rule" is designed to save your sanity, and applies to everything you will carry past the check-in counter. What you do is: count the number of adult hands you have in the party. Two fit adults = 4 hands, etc. Then count the carryon items you plan to take -- and count your children as "items" if they are too young to carry their own stuff, because you always need to keep at least one hand free per child. The number of "items" should never exceed the number of hands, except that each adult is also allowed to have a backpack. (Single-strap shoulder bags have to count toward the hands rule, though, because if you bend down, they tend to swing forward; I've seen a lot of toddlers knocked off their feet by a parent's carryon shoulder bag in an airport.) If your pile includes extra items, you need to plan to check them. Rolling bags count as a hand, too; pulling a rollaboard while pushing a stroller with the other hand is VERY awkward, and will drive you nuts. So, for example: if you have 2 adults and 1 young child, and a stroller, you can take 2 more carryon items. If 2 adults have 2 children and one stroller, one carryon item. If you have 1 adult and two children, plus a stroller, no carryon item, but the adult can use a backpack. Older kids who walk through the terminal have to be responsible for their own carryon items: Mama does not carry that teddy-bear for you, or that Elsa suitcase.
Oh, one other thing: when flying with a baby,
always take (in a carryon, not a checked bag) at least 24 hours worth of whatever supplies you would need for her if you were stranded in the airport. Diapers, wipes, lovie toys, spare clothes, special foods, etc. The airlines will tell you to take enough for the duration of the flight, but ignore that; 24 hours worth is the minimum, because if you get delayed by weather, you could be stuck in the airport that long, and airports do not usually have any diapers or baby foods for sale. Also carry on ziploc bags and spare shirts for each adult, in case your child throws up all over you mid-flight. (Airsick bags don't work for small kids; they can't warn you. It is best not to feed a child dairy for at least 3 hours prior to a flight. Dairy does not cause airsickness, but it makes the mess and odor a lot nastier if airsickness happens.)
