I'd offer even another scenario
1 adult at $139, 1 free child
1 adult at kids price $109
your 2yr old doesn't need a ticket
So $248
You can get the tickets from most travel agents, AAA, and even some Safeway stores, but I think they might only have the adult at the kid's price. arestravel.com had the best rates, but I don't see the kid's free on there anymore. Getawaytoday.com does still have both options though.