DO NOT, under ANY circumstances, TRY TO DO EVERYTHING.
You simply CAN'T and you'll end up tired, frustrated and disappointed. Make a priority list of what you want to do, and work down it, understanding that you won't get to do all of it. That way you can do what is most important to you and the family, and everything else becomes a benny.
WRT the disney character breakfasts - I would assume you would have that opportunity on the cruise, as well. I would do it there rather than at the park, since there is so much other stuff to do there.
The other best thing you can do, which is too late to do now, is to book your Disney trip the week before the shools get out for Christmas break. We took our kids out of school early in mid december in 2000. It was simply AWESOME because there were NO LINES. NONE. ZIP. We walked right into nearly all the rides and shows mentioned above with ZERO wait times (even phantasmic!). Well, maybe sometimes we had to wait a few minutes. Never more than 10, though.
If you have ever been to disneyland, the magic kingdom at Disneyworld will disappoint you. Many of the rides at DWMK are all SHORTER than their Disneyland twins. Pirates of the Carribean was especially disappointing in relation to the Disneyland version. However, if you have not been to Disneyland, you'll enjoy it just fine, since you won't have anything to compare it to.
My kids (at the time 12, 10, 8 and 6) all absolutely LOVED disneyquest in Downtown Disney. Its great because you can do it in the end of the day after the parks close, and it should be free admission with your park pass, though you would have to check on that. Inside is every coin-op arcade videogame ever produced, plus some that will knock your socks off and you have never seen before - (build and ride your own roller coaster, virtual river rapids ride, pirate ghost ship combat, buzz lightyear cannon-car game) - where you are IN the ship firing guns or in the raft pushing paddles instead of hitting buttons. Sounds expensive? It isn't becaase all those games are FREE with admission. We had a great time because we all got to do things together there. There's other stuff in there, but thats what the kids remember most.
http://disneyworld.disney.go.com/wdw/entertainment/entertainmentDetail?id=DisneyQuestIndoorInteractiveThemeParkEntertainmentPageWe'd eat dinner at whatever park we were at, then book on over to Disneyquest and stay there until it closed at midnight (I think).
Yeah, the kids got tired, but I wasn't gonna force them away - it was a once in a lifetime trip and I wasn't going to artificially impose rules made for the outside world. I did end up carrying my 6 year old around a few times, though.

And yes, understand that the money you've paid, is only the first installment - you are going to spend a LOT MORE when you're there. Just bite the bullet and spend and don't look at the bill until you get back to the real world.

BB