Last year, we were there w/ our 5 1/2 year old DD & our 3 year old (2 months from being 4) DS.
At MGM -
We watched the Beauty & the Beast show & the Voyage of the Little Mermaid Show which they both enjoyed - Little Mermaid probably more than Beauty & the Beast.
That was really all we did at MGM... (MGM was our "easy" day, so, after lunch, we went back to our FW cabin for naps. Our kids weren't familiar w/ the characters of the other shows, so we skipped those shows)
Later, that afternoon, we watched the Stars & Motor Cars Parade which they enjoyed - lots of good character interaction at this parade I thought.
And, that evening, we saw Fantasmic which they also liked (although, at first, our DD was a little leery of the fire & some of the villians).
We ate lunch at Toy Story Pizza Planet which was nice quick lunch for kids, and we saw Buzz, Woody, & Jessie at Al's Toy Barn.
At MK, we did the following:
The Barnstormer - this was our "test" roller coaster. DS liked it much better than DD, but our DD did ride it & wanted to ride it again...
Big Thunder Mountain - DS loved & DD hated (we only rode it once - I thought, since they both liked Barnstormer, they would like it - but DD didn't like it AT ALL.)
Buzz Lightyear's Space Ranger Spin - LOVED! We had to ride this one several times - DD liked it as much as DS
Carousel of Progress - nice break!
Cinderella's Golden Carousel - loved, of course!
Donald's Boat - very fun & refreshing
Dumbo the Flying Elephant - LOVED (because of the lines, we only rode this one once, &, as it was my DS's absolute favorite, I wish we had ridden it more)
The Haunted Mansion - we rode it, but, although they were both "brave", both said they didn't want to do it again
It's a Small World - loved, as irritating as the song is, we rode this one several times - it was DD's favorite
Jungle Cruise - they enjoyed; nice, funny ride - not scary
Mad Tea Party - lots of giggles on this one
The Magic Carpets of Aladdin - fun ride
The Many Adventures of Winnie the Pooh - I thought this ride was extremely well done - I was fascinated by all the details - both our kids really liked it
Mickey's Country House - fun
Mickey's Philharmagic - this was our kids' favorite show - they still talk about it
Minnie's Country House - fun - they were escorted through by Donald Duck himself
Peter Pan's Flight - we only rode this one once, but would definitely do again - we all loved it - the line is extremely long, so ride it (along w/ Dumbo) 1st thing
Pirates of the Caribbean - DS liked it - DD tolerated it - by the end, she was laughing though
Tomorrowland Transit Authority - nice ride for a break
Toontown Hall of Fame - get there at rope drop! The characters come out & then escort the children through Mickey & Minnie's House. Donald Duck grabbed our DD & DS hands & led them through. While we waited for rope drop, Pinochio came out & interacted w/ the kids.
Walt Disney World Railroad - we love trains in our family, so this ride was perfect for us
Share a Dream Come True parade - they really enjoyed this parade, but we had to wait forever in the hot sun...
SpectroMagic evening parade - they LOVED this parade!
Wishes fireworks - PERFECT, PERFECT, PERFECT! (Even our DD who doesn't like fireworks normally says that she loves Wishes)
We purposely skipped Space Mountain, Splash Mountain, Stich's Great Escape, & Snow White's Scary Adventures.
The restaurants we ate at while at MK were the following:
Liberty Tree Tavern for dinner (Goofy, Pluto, Chip, Dale, & Minnie)
Crystal Palace for lunch (Pooh, Tigger, Eeyore, & Piglet)
CRT for breakfast (Cinderella, Belle, Wendy, Mary Poppins, Snow White, & Sleeping Beauty)
All were very good & I would definitely recommend.
The #1 tip for MK w/ young children is go directly to Fantasyland & get there early.
we only have 2-1/2 days so i want to make the most of our trip and do things that she will enjoy including rides and not waste time walking around aimlessly picking rides that she won't enjoy. she isn't into scary rides or too high rides 
. if anyone has any recommendations it would be awesome. i'm doing research but at the same time it's nice to know what others kids have liked personally. from what i've seen most recommend that we should spend 2 full days of our 2 1/2 at MK. i think we'll spend the 1/2 day at MGM because she likes all the characters shows. so again, any specific rides or attractions for 4 y.o. would be great as i'm trying to compile a list and make a plan to make the best use of our time. thanks for any input 
