From KC, I believe that Southwest and Midwest Airlines are the only two that have nonstop flights. They both fly direct into LAX. You can go to SNA/John Wayne, but it may cost more, and you will definitely have a connecting flight. So you'll need to think about what you want -- cost vs. connecting/direct flight vs. distance to DL.
I'm not sure if Midwest even has rates published through your time frame. I know they have them out through July, but the price is a little higher than I'd like right now. From what I've read on transportation boards, 3 months prior is about the right time to get a good price on flights. Southwest fares and schedules are published about 3 months ahead, but will probably be the least expensive option. I'm just not sure about doing Southwest out of LAX and leaning towards Midwest in order to get seat assignments and not worry about having to check-in early for seating.
