are you driving there or flying? If flying, it is inexpensive to stay at one of the Disney resorts because of all the perks you get: free transportation to and from the airport -- they take your luggage for you so there's no waiting at baggage claim -- and they take them directly to your room for you. So you can literally hop off the plane and go straight to the parks.
Also, if you are a resort guest there is bus/boat transportation to/from the parks to your hotel. There's really no need for a car rental. No parking hassles at the parks or parking fees.
And if you're a resort guest you get to stay in certain parks earlier than opening/later than closing -- there's a schedule of which parks have early magic hours or late magic hours for resort guests -- that means you can ride those most popular rides with shorter wait times during those times!
So there are some great perks.... have you seen the value resorts -- like Disney's Pop Century Resort. I think the value rate is $82/night for a standard room; regular rate is $99-109. I think in October, you'd be going at either a regular time or a value rate time. Summer and holidays are peak prices. Christmas time is actually a very expensive time to go!!
Other value resorts are the All-Star resorts (All-Star Movies, All-Star Music, All-Star Sports) and they are soo cute for kids!! Look at the pics on the website below.
Go to allears.net for more tips/reviews.
Also -- the Magic Kingdom isn't to babyish for any age -- my husband and I loved it!! Really there's something for every age!! Go to that website for the rides you should go on. Also the best book out there is: Passporter's Walt Disney World! Gives lots of info about every park and that book has the best maps -- better than Disney maps that they hand out at the parks! This book also gives the age recommendations of each ride/height restrictions so you can plan out your day better. At Magic Kingdom, there's Big Thunder Mountain Railroad rollercoaster; Splash Mountain log flume; The Haunted Mansion - scary!!; Space Mountain (rollercoaster in the dark); Stitch's Great Escape; Tomorrowland Indy Speedway (bumper cars).
Also -- For an older boy that loves to be scared -- I would highly recommend going to Animal Kingdom and riding the Dinosaur ride -- OMG!! I was scared out of my pants!! Lots of HUGE dinosaurs roaring at you in surround sound - in the dark! The older kids loved it! My poor 5 yr old -- he was shaking a bit! I think it was too much for him.
At Disney's Hollywood Studios -- go on the Aerosmith Rock 'n' Roller Coaster; and of course the Twilight Zone Tower of Terror (that's the elevator ride that goes up and down over and over again).