Erin,
Those are all great questions. With a first trip, and with children as young as yours (similar to mine), the Magic Kingdom will see a lot more of you than the other parks. But with such a long stay, you have plenty of time to see them all. Of course in each park there is plenty for you to do. Here is how I would break up your time;
- January 29 - Arrival Day
- January 30 - Magic Kingdom (all day)
- January 31 - Magic Kingdom (am) / Typhoon Lagoon (afternoon) / Magic Kingdom (pm)
- February 1 - Animal Kingdom (am & afternoon) / Downtown Disney (pm)
- February 2 - Hollywood Studios (all day)
- February 3 - Epcot (all day)
- February 4 - Typhoon Lagoon (am) / Hollywood Studios (pm)
- February 5 - Magic Kingdom (am) / Epcot (pm)
- February 6 - Magic Kingdom (all day)
- February 7 - Departure Day
Note that I have you at Typhoon Lagoon for a water park. Blizzard Beach will be closed then for refurbishment, which is an annual thing. Both water parks would be great for your family, so no loss here.
Also remember that for most days, even ones shown here as "all day" at a park, should include some rest time back at your resort. Naps, swimming if the weather is OK, whatever. But let your kids get back their energy.
So write me back with any follow up questions! Glad to help further, including dining recommendations, alternative plans, special occasions, you name it!
Have a magical vacation!