Hi Carrie!
Crowds do generally grow on the weekends at Magic Kingdom (as well as all the Parks). But with it being February, I don't anticipate the crowds to grow to the point that you would leave Magic Kingdom. Unless next year happens to be an unusual circumstance, you should be fine sticking around the weekend...
So, sounds like you have a 4-night/5-day deal? For the Parks, try Epcot on Wednesday, Hollywood Studios on Thursday (Thursday at HS will have Fantasmic), Animal Kingdom on Friday, and Magic Kingdom on Saturday. Then, if you have time on Sunday, you can shop, spend a little time at the resort, etc.
Have a great time on your February trip!