Being from the north myself I too find it hard to pack for a Disney winter vacation!
My best advice to families heading south in February is to think layers! Orlando can have huge temperature swings where one day it is very cold with frost and then the next warm and sunny. The average temperatures for February are: high of 72 to low of 51. These are just averages and we never know what tricks mother nature will play on us!
I suggest that you have wraps for the early mornings when you head out to the parks as it will be cool. During the day if the sun is out you will definitely want to shed these. Then once again when the sun goes down in the late afternoon and early evening you will need the wrap again. Bring a lightweight bag to put the wraps in during the day. If not you will start a collection of Disney sweatshirts as our family did for years until we learned our lesson to be prepared!
I would bring a combination of shorts and long pants. Definitely bring the swim suits as all the Disney pools are heated. Your children would hate to see one of the great pool areas and not be able to at least try it! When visiting this past December, which has a similar temperature average, I wore capris and short sleeve tops with a light wrap and was very comfortable.
About five days before you go check the weather channel website,
www.weather.com, and look up the Orlando weather. You will be able to see the 7 day forecast and get a better idea what will be happening during your visit. Have a great vacation!