Start your airfare research on a website that compares pricing on multiple airlines, such as
http://www.hipmunk.com/ and/or
http://www.kayak.com/
Also check Southwest separately because Southwest is not properly included at the websites above.
When comparing prices, factor in luggage fees and potential change fees. Southwest often comes in higher than other airlines, but when you factor in luggage (2 bags free per passenger) and flexibility, Southwest can have the advantage. JetBlue offers 1 bag free per passenger.
Although nonstop flights save time and eliminate the possibility of a missed connection, you can often save money with connecting service, and you'll have far more airlines to choose from. (Try to avoid connections of less than 1 hour, even if i's a "legal" connection according to an airline's website.)
You have several destination airports to choose from. There can be significant price differences. The most convenient airports (in order of convenience) for
Disneyland are:
1. Orange County (SNA)
2. Long Beach (LGB)
3. Los Angeles Int'l (LAX)
4. Ontario (ONT)
(In the list above, 3 and 4 could also be flipped because ONT is a smaller airport that's easier to get in and out of than LAX.)
You have several departure airports to choose from: IAD, DCA, and BWI. Sometimes driving an hour to a different departure airport is worth it.
Be flexible regarding the days. Sometimes flying a day or two earlier or later can mean much lower or higher pricing.
If you find a good fare on American Airlines, put reservations on a free 24-hour hold on
AA.com and buy enough $300 gift cards for $269.99 each at Costco (if available at your Costco) to pay for the tickets.
I hope you find an acceptable airfare and that you have a good trip.