Yes, we drove it last year on our big family reunion Thanksgiving trip! It wasn't too bad. We also stopped in the Savannah area - somewhere off I-95- I think it was technically Port Wentworth, GA. Right off the interstate, it worked out great!
Hmmm...snacks in the Studios and at AK? Are you on the Dining Plan? If so, there is a thread right here that has a whole bunch of what is considered a snack in all of the parks....pretty thorough!
http://www.disboards.com/showthread.php?t=2067447
My kids love Mickey bars, Itzakadoozie (giant popsicles) and Popcorn - which you can get at all the parks. The Studios have these giant sweet pretzels or cheese-stuffed pretzels that are supposed to be very good, and I have heard great things about the muffins at Starring Rolls. The AK has some good stuff at Dino Bites in Dinoland (over near the Boneyard area) - they have the big chocolate chip cookie ice cream sandwiches like they have in the MK, and really good Rootbeer Floats.
You'll be amazed at how many things your daughter can go on at her age - especially at the MK. The whole entire Fantasyland section will be fabulous, in Toontown she might be big enough for Barnstormer (35" is the min), but lots of characters over there. If she isn't frightened (I like to call it "Scooby-doo" like scary to my kids) she could go on Haunted Mansion. Over in FL, she might enjoy exploring Tom Sawyer Island and in AL, the Jungle Cruise and the Magic Carpets are big hits with my kids. TL has Buzz Lightyear, and Monsters Inc, and I'm sure she would love the TTA!!! It's one of my girls' favorite rides!! At AK, Triceratop Spin is just like Dumbo, the Safari is great and all the trails where she can see animals are a lot of fun! There is a little train that will bring you over to a petting zoo type thing that also has animal exhibits and occasionally you can catch the CMs doing procedures on the animals if she is at all interested in that kind of stuff. I prefer not to go to petting zoos, but that's just me.
The Studios has Toy Story Mania!!!! Oh how fun that ride is!! They have the Playhouse Disney show and the Little Mermaid and Beauty and the Beast shows - a lot of shows basically! That park has a lot of character spots though, so if she enjoys that, make sure to pick up a times guide when you enter and see when/where her favorites might be coming out. But get there early for TSM if you want to ride it more than once!!
Which leaves Epcot. For a 3 year old, I would definitely do Figment, Finding Nemo, Turtle Talk with Crush, there is Living with the Land right near Soarin if one of you wanted to ride that, the other could take her over to ride Living with the Land, and then you could switch (because Soarin is fabulous - make sure not to miss it!). In the World Showcase, there are the two boat rides - Maelstrom (Norway) and Gran Fiesta Trio (Mexico) which my girls like. They have the Kidcot stations at each country too, so make sure and check those out. The CMs there are usually very interesting.
Have a great trip!! Let me know if you have any questions - I love to try and answer stuff! (And a lot of my readers are way more knowledgeable than I am, so speak up trip report readers if you have any suggestions...especially on the snacks...)
Oh, I just thought of my absolute favorite snack...the make-your-own-treat at Goofy's Candy Co in Downtown Disney. Slow to make, but really delicious!
Sara