Too many to name! LOL! My kids were that same age the last time we went and they loved pretty much everything geared towards their age...
: You can't go wrong here!!! Buzz Lightyear, the cars, TTA, the tea cups, Goofy's Rollercoaster (the 3yo wasn't wild about it, but it was right up the 5yo's alley!)... It's a Small World, Pooh, Peter Pan, Dumbo, Philharmagic show, Splash Mountain, Big Thunder (good for the 5yo), Aladin's carpet, Tiki Room, and the Jungle Cruise. Monster's Inc will be opening very soon (if it's not already) and that should be a big hit too! Don't miss the 3pm daily parade and the Wishes fireworks show. Be sure to pick a day when the Spectromagic parade of lights is happening- they'll love that too!
: Little Mermaid show, Playhouse Disney, Beauty & the Beast are perfect for girls. But the Indiana Jones Show, Lights Motor Action Show, and Star Wars (for the 5yo) are neat too. Don't miss the Fantasmic! and the Stars & Motor Cars Parade at 3pm daily.
: Don't miss Crush the talking turtle (so cool) and the new Nemo ride- along with the entire Living Seas Pavilion (LOVE IT!). The little ones also might like Figment. Living with the Land and Spaceship Earth may be "too old" for them, but they can ride them still. The 5yo will love Test Track (at least mine did- it's all he talked about!).
: Safari Ride (go early when the animals are out), Lion King Show, Rafiki's Planet Watch (see the live animals), the Bird Show, It's Tough to be a Bug (might be frightening to the littlest- hold him/her), lots to do in Dino Land, and the daily parade at 4pm.
They might consider a princess character meal at Cindy's Castle or Akershus (in the World Showcase) or the Grand Floridian with Mary Poppins & Friends *they also have a "tea time" at the GF- look into that!
The kids should have a great time at the Poly pool too- so build in some relaxation time there.
And like you said, the Boutique in DD is perfect for girls.
Also encourage your friends to go to Disneyworld.com and take advantage of the FREE maps... They can "add attractions/shows/dining" to a customized map, save it and Disney will send a full-color, keepsake quality map to them free. There are maps for each of the four theme parks. COOL!!!
I hope that helps!
They are going to have a GREAT, GREAT TIME!