Skip Stitch, unless you have a diehard Stitch fan in your group. This was the first ride we hit at MK and we all hated it (DD's 10, 11 and DH 32). I thought it was pointless. If you must do it, grab a FP or go when there is a short wait time.
My DD's LOVED Carousel of Progress. We had to do it twice. And it's a nice attraction to sit back and relax. It never appeared to have much of a line. Fine for the 4 year old.
Fantasyland, by far, seemed to be the busiest land in the park. Or maybe it was because it was a sea of strollers. We found a great time to hit this land was during the fireworks. We walked right on Pooh, Small World, Snow White and Cinderella Carousel. Snow White may be questionable for a 4 year old, it is a little on the dark side, as far as a Fantasyland attraction goes.
Plan to spend some time in Toon Town, this is perfect for small children. We didn't spend much time there, but it was really busy.
Anyone who likes roller coasters will enjoy doing the Mountain Trifecta. This is hitting Splash Mountain, Space Mountain and Big Thunder Mountain in one day. This was probably the highlight of our trip. It's a little tricky to do all in one day, as these are the most popular rides in all of MK. Again, we took advantage of the fireworks to be able to get on these rides with a small wait. We had a FP for Space, then took the Train to Frontierland, rode Splash with about a 10 minute wait, walked over to Big Thunder and had about a 5 minute wait there. What was really cool was seeing the fireworks while riding Big Thunder. A true Disney moment. I should say we were not able to do the mountains and Fantasyland during one night of fireworks. This was over 2 nights, one being an EMH night and the other was open to all until 12am.