Hi Angela!
First, congrats on your 1st trip! Be prepared to be dazzled at the "Funnest Place on Earth!" :-)
Bringing both my son and daughter at pre-school age (son as early as 18 months), I certainly understand your concern about them having as fun a time as everyone else. Well, no worries! Your younger children will be just as, if not more so thrilled as everyone else!
Here is a snapshot of rides, activities, and places my pre-schoolers thoroughly enjoyed at the parks:
Magic Kingdom
- It's A Small World!
- Buzz Lightyear's Space Ranger Spin
- Dumbo Ride/Mad Tea Party-Fantasyland (these were 2 of his favorites)
- Mickey/Minnie House-Toontown Fair
- Peter Pan's Flight
- Disney Railroad
- Magic Carpets of Aladdin
Epcot
- Imagination Pavilion
- Innoventions
- The Seas with Nemo and Friends
- Kidcot Fun Stops at World Showcase
- Journey Into Imagination With Figment
Animal Kingdom
- Kilimanjaro Safari
- The Boneyard
- TriceraTop Spin
Hollywood Studios
- Playhouse Disney-Live on Stage!
- Honey I Shrunk the Kids Movie Set Adventure
- Toy Story Mania
This is by no means a complete list, but hopefully shows you that Disney has a lot of things for even our youngest. All of these items above my kids had a terrific time doing!
Have a super magical time on your first trip!