I think other than Magic Mountain, there's not any touristy type things in the Valencia/Santa Clarita area. If I was planning the trip for me, I'd try to fly into Burbank (if it's 3 stops, I'd suck it up and fly into LAX or Ontario), start at the north with visiting/touring the school and going to Magic Mountain if you want. Spend the night. The next day I'd check out and go south to Universal, spend a few nights. If I was from the east coast and this was my first time out here, I'd tour the LA area, Grauman's (or whatever it's called now) just to see the footprints, Rodeo Drive, Pacific Ocean, Warner Brothers studio tour or whatever you are interested in. Then I would check out and drive south and check in for
Disneyland. 3-4 days minimum now for DL. Then I'd try to fly out of John Wayne or LAX. (or if you have more time, continue on to San Diego for a few more days and fly out of there).
Honestly from Santa Clarita to Disneyland, it's straight all by I-5. I was going to say that I'd rent a car but in all honesty, it's a necessity. It will also allow you all to drive around the immediate area to show your daughter the way to Target and such.