Hi!
We were at Disney twice for Valentine's Day, 1998 and 2001. The first trip our kids were 6yrs, 3yrs and 15 months. the second trip they were 9,6 and 4. I don't remember anything special at the parks but in '98 we had breakfast with the characters at Cape May Cafe and it was decorated nicely for the holiday. Even the pastries had pink icing. Our 3 year old asked where Minnie and Mickey were. Our 6 year old's reply..."I think they're probably on a romantic date". The memorable part of the 2001 trip was that we booked an adjoining room for my inlaws during our stay. They went home early and my husband and I had our own room for Valentine's Day! That was some unexpected Mickey magic!
Oh, and for both trips I made out valentines at home to the kids from their favorite characters. I set them next to the door on Valentine's day morning as if they had been slipped under. The kids really enjoyed opening valentines from their Disney friends. Sorry I went on so long. Have a great trip!