Janet:
I like to think that two days at Disney--even if I'm stuck in my hotel room--are better than staying at home, so keep in mind that no matter what you decide to do, you're going to be delighted.
If I were in your shoes and only had two days, I would consider visiting Magic Kingdom and Disney's Hollywood Studios considering the ages of your children. At the Magic Kingdom, your daughter may not meet the height requirement to ride the "mountain" rides of
Space Mountain, Splash Mountain and
Big Thunder Mountain. With that in mind, spending two days there might become tedious with splitting time between what your son and daughter can or cannot ride.
Additionally, Disney's Hollywood Studios features the more current characters that many children today think of when you say Disney. From Doc McStuffins to Princess Sofia, Buzz Lightyear to 'Mater from Cars, your children might actually identify more with the shows and characters in this park. There will still be a few height requirements for
Rock 'n' Roller Coaster and
Tower of Terror, but like the Magic Kingdom, your children will find much in both parks to make memories.
Wishing y'all a magical vacation!
Whitney