1st, welcome to the disboards!!! You are going to have a great time!
Christmas is a very busy time and if you provide the exact dates you are traveling, I am sure everyone would be happy to offer their opinoins!
It sounds like you have decided where to stay and will have a kitchen. That is great, particulary since you like prefer to eat "at home". You can take drinks and snacks into the parks, just not a big ice chest. Plan on having breakfast at the condo, pack snacks (possibly lunch?) and drinks. Are you going to stay at the parks all day or do plan on leaving before dinner?
What you should pack will depend on where you are from. The average high will be in the 70's and the average low will be in the 40's/50's. For us, that means long pants/capris with SS t-shirts and jackets. (It is 40 with wind and rain here in north Texas today and I am freezing!!!)
Plan to arrive at the parks atleast 30 minutes before they are scheduled to open. Mornings are going to be the least busy time of day.
How many days will your family be spending in the parks? Each park has activities for kids of all ages! The Magic Kingdom is a must do!
There might be a "Mickey's Very Merry Christmas Party" happening while you are there. People on the boards refer to it as "
MVMCP" for short. At Disney Studios, make sure you see the "Osbourne Lights". There are several things happening at Epcot, depending on the day. I cannot think of anything special at the Animal Kingdom, but I could be wrong.
I would strongly encourage you to purchase a 2007 guide book. I like the Unoffical Guide, but it may be too much information. A guide book will explain the fastpass system and lhave ots of other great information!