alaska airlines should offer free kids tickets for every adult one you buy. it's on their website. personally, i think the park hotels are worth the extra money. we usually go for 4-5 days, buy 3 day park hopper tickets, and enjoy the rest of the time at the hotel. the hotel pools are awesome and there's tons to see in downtown disney.
one $ saving suggestion- for dinner, order pizza and have it delivered to your hotel. it's MUCH cheaper than eating at any of the disney resort restaurants and you don't have to drive anywhere to get it.
i always book through AAA and save bigtime compared to expedia. sounds like you're gonna have fun- we're anxious for our next disney vacation!