Hi Amy,
The Walt Disney World Resorts are always good to visit!! The only time it may be more crowded is during President's week when many schools have a week long vacation. Otherwise, you should see lighter crowds.
The weather can vary in February. I have been in January when it has been 80 or 30! I always check the weather online before I go so I know what to pack. The pools will be open and are a constant 82 degrees along with all the water in the water parks except for Shark Reef which is at 78 degrees.
For a family of five, you have limited choices as only certain
resorts can accommodate you. I love the All Star Music Family Suites, Port Orleans Riverside and Beach Club as my favorites at each category. For tickets, I would recommend skipping the park hopper and concentrate each day on a park. This way you can take the extra money from hopping to put towards your room. Look in the fall for offers and promotions including signing up on Facebook and Twitter.
As for activities, I would schedule one character meal or dinner show like Hoop Dee Doo Revue because it is fun. I would also ride Kiliminjaro Safari, Toy Story Mania, Soarin', Mickey's PhilharMagic. If your children know about the trip, you have them look at the attractions and pick three at each park and ride them. This way everything else is a bonus.
Wishing you a magical vacation!
Beth