Given any amount of advanced planning, you have AMPLE opportunity to find a good/cheap flight. Southwest usually has the best deals, but I don’t know what airport you’d come out of, so I can’t tell you for sure. For all non-Southwest flights, use Kayak.com to check fares and farecast.com to see the best time to buy them.
There aren’t many really special tricks to this, other than to know that if you book far enough out, you might even be able to get refundable tickets for not too much more than the standard non-refundable ones. This means that if you buy them and the costs DROP, you can buy the cheaper ones and return the more expensive ones. Then again, that’s a lot of time/effort and playing around. You also know your family best, but I usually try to go for morning direct/non-stop flights.
I choose the morning because then you have the whole day at the parks without having to pay for a night simply to sleep in Orlando. If, however, you need to go at night, stay at the Airport Hilton that night and travel to the parks in the morning, unless you get a $50/night room “on property” (which is possible).
Air travel is also made a little more complex these days as a result of the TSA. There’s nothing special about going to Orlando (MCO) or Los Angeles (LAX) from any other particular airport. But airports still recommend arriving at your departure point about 2 hours ahead of take-off to allow ample time to get through security. With kids, this process has actually gotten worse in the last few years, with pat-downs and other security measures beyond a metal detector and x-ray process. Be sure to check with your airline if you need any special accommodations, such as bringing frozen breast-milk or a stroller (some airlines consider it chargeable baggage, others don’t).
Arriving in Orlando is also fairly non-eventful. All arrivals require a tram trip (not “the” monorail, but some kids will think it is) to the baggage area and it’s possible that you’ll see Disney Cruise Line Cast Members standing by to direct Cruise passengers on where to find their busses. You can’t miss them – they usually have large puffy “character gloves” on their hands. But these CMs are able to assist you, too, in the event you need help.
For LA, some folks prefer to travel through the Bob Hope Burbank Airport (BUR) instead of LAX. Either will get you to California and on your way to Disneyland, it’s just that some folks believe that Burbank is quicker because it’s smaller. Distance-wise, it’s about the same. Likewise, some individuals prefer to fly into the Sanford International Airport (SFB) in Orlando, instead, too. In fact, some claim that it’s much cheaper, even if they have to rent a car.