Hi Cassie and welcome to the Mom's Panel!
There is a tool available on the Walt Disney World website which lists all of the available attractions at each of the parks which can be found
HERE
To see which attractions would be suitable for your almost 3 year old you need to click on 'Recommended Ages' on the left hand side of the page and then select 'Pre-Schoolers'
You are also able to filter the attractions by 'Height' in the section underneath 'Recommended Ages'
You will be suprised at just how many things that your child will be able to enjoy during your visit.
There are attractions at every park which cater to young children. I would suggest that you look through the sections for each park on the Walt Disney World website
HERE to decide which other parks would be most enjoyable for your child.
Wishing you all a magical holiday!