Hi Ritva!
It makes me so happy to think of you bringing your 9 month old with you to Walt Disney World. It's fun to start instilling love of the happiest place on Earth when they are that young! Plus you'll create memories that you'll cherish forever.
I've always found there were so many attractions that are "litlle ones" friendly, that I never felt like there wasn't enough to do. In fact, I found that there was so much to do, that I needed more time in the parks to do it all! Obvious rides that are out of the question for a baby that young are those such as Space Mountain, Rockin' Rollercoaster, Mt. Everest, and Test Track. In fact, if you go
here, you'll find information especially put together for families traveling with little ones, and on the right side of the page is a pdf with attraction height requirements. Any attraction left off that list can be enjoyed by guests of
any height! You'll want to use your own Mommy instincts to decide if your little one will enjoy the Haunted Mansion. My children did, but it's not for every child.
On that same page, be sure to check out the Magical Beginnings Park Maps, which highlights attractions that are geared towards little ones. If you'd like more help, feel free to submit a follow up question.
Have a magical vacation!