Peter Pan is your number one priority if you don't have a fastpass for that. I'd start there for sure. If characters are important for you, go to Ariel's Grotto next. Otherwise skip that and do Winnie the Pooh which also gets reasonably long lines. Then I'd hit Little Mermaid, Dumbo, and Barnstormer in no particular order. Check out Pete's Silly Sideshow if characters are important to you. Then I'd go back to the Mad Hatter's Tea Party, the Regal Carousel, Small World, and finish out with Mickey's Philharmagic.
So...
1. Peter Pan
(optional step: Ariel's Grotto)
2. Winnie the Pooh
3. Journey of the Little Mermaid
4. Dumbo
5. Barnstormer
(optional step: Pete's Silly Sideshow)
6. Mad Hatter's Tea Party
7. Regal Carousel
8. It's a small world
9. Mickey's Philharmagic