I need air travel advice.?

In early Oct. I'll be needing to fly from Tucson, AZ to El Paso, Tx and want to know of any discounts, or suggestions. What's the absolute best and economical (not too risky, though, will be traveling with two children 7& 12) way to go? Southwest seems cheapest, but are there other ways I can get discounts? Thanks!
One more thing: I for sure want the kind of tickets that I am guaranteed seats, not the kind where there "may not be any available seating"

southwest is great! i've flown them before! i'd definitely recommend it!!

Don't fly southwest. They herd you in like cattle, some of their stews think they're comedians, they're not. I flew sw to orlando last year and I'll never fly that airline again.

AVOID southwest...very little space and its not assigned seating, its first come first serve, sooo try continental..that's the only airline i'm going to suggest 'cause its the best US carrier..hands down..just monitor their prices they like to drop them suddenly..i got a plane ticket to OAK for $193..it was cheaper than southwest's $99 one way!