A LOT has changed since '94.
MK - Fantasyland
Snow White's Scary Adventures is now gone and is being replaced with a Princess Meet and Greet (not completed)
The "New Fantasyland Expansion" added a new "french inspired" Be Our Guest restaurant where you can eat inside the Beast's Castle, a show/meet and greet with Belle, a Quick Service "Gaston's Tavern" with unique offerings, and the Little Mermaid Ride. There is a Mine Train ride coming, not it's not completed yet (and probably won't be during the time of your trip)
Mickey's Starland has been removed and replaced with Storybook Circus...which included several changes / additions.
1) A New fountain attraction based on Casey Jr.
2) Dumbo ride was moved over there from behind the castle, and has been doubled.
3) Goofy's Barnstormer (now called Great Goofini) is a kids roller coaster (very fun!)
4) Pete's Silly Sideshow (a meet and greet)
Mr. Toads Wild Ride has been shuttered and replaced with Winnie the Pooh.
20,000 Leagues under the Sea may have already been closed on their last trip, as it closed in '94, as I recall...not sure exactly when though. But, anyhow, it's gone. Likewise, the Skyway is also defunct.
Mickey's PhilharMagic is an entertaining 3D show that plays where Magic Journeys / Legend of the Lion King used to be.
MK - Adventureland
A spinner ride similar to Dumbo has been added outside the Tiki Room that is themed off Aladdin.
The Tiki Room will be very similar to how they'll remember it in '94, but the show is a bit shorter
MK - Main Street
Center Street has been carved up into expanded shops, but otherwise the EXTERIOR of Main Street will feel very similar. However, the interior has been almost all converted into one massive shop / eateries, including a Starbucks which recently opened. Gone is the Penny Arcade, gone is the dedicated Mickey Mouse theater (replaced with an art gallery, though it still does play cartoon shorts in there). If you want to play an old penny arcade machine, two of them (maybe more, but I think just two) were moved into the Main Street Train Station.
Also, Mickey Meet and Greet has been added.
MK - Tomorrowland
The Skyway has been removed.
Mission to Mars (which probably would have been closed in 94 for conversion to ExtraTERRORestrial Alien Encounter) has been revamped again to include Stitch. A word of warning, this is a fun show, but smaller kids may freak out. It's rather intense.
Dreamflight has been removed and replaced with Buzz Lightyears Space Ranger Spin, a shooting dark ride (lots of fun).
The Monsters, Inc Laugh Floor has been added, which is a unique "stand up comedy" style show starring the characters from the movie interacting with the crowd.
MK - Frontierland
The canoes are gone, but Tom Sawyer Island is still accessible!
Otherwise, this area hasn't changed much.
MK - Liberty Square
This area hasn't changed much...though, the Hall of Presidents has been updated (of course) and the Haunted Mansion got a new interactive queue and new hitchhiking ghost effects.
EP - Tomorrowland
This is where I think you will notice the most drastic changes...
The entrance to EPCOT has been dramatically redone, removing the large "crystals" and replacing it with granite (I think) features that allowed guests to purchase plaques with their names and pictures on them.
Spaceship Earth has been through two show updates since 94 (depending on when you went in '94). If you remember Cronkite doing the narration, then you went before August...if you remember Jeremy Irons, then you went after...
Anyhow, now the new show has interactive features build into the ride vehicles, an updated presentation / play area after the ride ends, updated characters and decent scenes, and is narrated by Judy Dench.
Universe of Energy has been reworked, with several major changes (and some minor). It is now hosted by Ellen Dejeneras (sp).
Horizons is closed, and has been replaced (building and all) with Mission: Space, which is a simulator ride of a mission to Mars.
World of Motion is now closed, and has been replaced by Test Track.
Imagination is showing Captain EO (though, you may remember Honey I Shrunk the Audience, that film started in mid 94). The upstars Imageworks is now closed, and has been moved downstairs at the exit of the ride. The ride has been completely redone. Dreamfinder is now gone, and replaced with Dr. Nigel Channing and a largely animated Figment.
The Living Seas now has some new buddies. A dark ride with Nemo and Friends, some zany seagulls outside, a meet and greet with Crush the Turtle (WORTH seeing, quite fun), but otherwise hasn't changed much inside, outside of new color schemes and some Nemo themes.
The Communicores are now called Innoventions, and have been drastically reworked. Innoventions opened in 94, so you may remember them, but even if you do, they've changed a LOT since the 94 incarnation.
The Land pavilion still has the boat ride, but it no longer has a human narrator in the last part of the ride.
The Food Court has been completely redone.
Kitchen Kabaret / Food Rocks has been removed and replaced with a new (very thrilling) ride called Sourin'.
Symbiosis, which used to play in the upstairs theater, has been replaced with Circle of Life: An Environmental Message (based on Lion King).
The Odyssey restaurant closed in '94, and has never been reopened for general use.
The Wonders of Life pavilion was closed in '07 and has never been reopened for general use. The rides and attractions in there are now defunct.
In the Mexico Pavilion, El Tempo Del Rio (The boat ride) has been replaced / updated with Donald and the Three Caballeros.
China's Circlevision Theater has gotten a new movie.
France got a few new shops and restaurants, as well as Ratatouille (well, a robotic version of him) who makes table visits at Les Chefs de France
The Freedom Boats don't run as much as they used to...and the busses are gone.
The Nighttime Show (Illuminations) has been replaced / updated. It's awesome!
Canada got a new movie and a new outdoor show / live band (Off Kilter).
Morocco got a new outdoor show / live band (Mo'Rockin)
Italy got two new restaurants, and the old restaurant that was there is now gone.
So, that pretty much sums up EPCOT...lot...isn't it! Told you it would be! But, oh I almost forgot...
They added an interactive game for World Showcase called Agent P. It's based on the characters from Phineus and Ferb. It's a load of fun for adults and kids alike. Check it out!
<whew> This got a lot longer than I had expected...I think I'll save Hollywood Studios for another post in a bit as I need a break, and there are some major changes / updates there as well...
Cheers!