First I concur with Flutterby. Just because you are tall enough for an attraction does not = temperament to handle said attraction. Example; About 20 years ago I brought my daughter to WDW (First Time), at age 4. We spent our 4 days for the most part in the Fantasy Land area. We skipped going at age 5. Even though she was tall enough. I knew that she was not ready to advance onto the attractions that require a taller person.
At age 6, she had grown emotionally, to where I felt comfortable to take her on the "Big Person" attractions. Albeit, she was still apprehensive or I should say, "inquisitive". She would ask, "Is everything going to be okay?". That was her way of overcoming her fears/phobia's.
You know you have arrived at that point, when they ask to ride SM 4 times in a roll. Or ToT, 6 times in a row. You just have to know and understand the young one's, ability to handle the unknown. One caveat. We all misjudge things from time to time. What we perceive they can handle. Then reality steps in and we are reminded.
I had such an experience. For those of us that recall the AI attraction. I brought my daughter on that at age 6. Not my best moment/decision.

I horrified her for years to come.

I did try to make it up to her with presenting her with a "Skippy" doll. Even when she was age 9, she still would not go on it again. Many years later and many trips back to our "Happy Place" we're able to laugh and recall a time when I misjudged the situation.
My next plans are to take my grandson to WDW in early December. He will be 15 months. In dog years he will be adolescent. But he is most indeed human. So, we are planing on seeing the lights and beauty of the Christmas season. With maybe a ride or two. "It's a small world", Prince Charming Regal Carrousel, Enchanted Tiki Room and the spirit of Christmas. Seven Dwarfs Mine Train. Just kidding. Maybe for me or my daughter and Son In-Law.
Anyway, good luck on your coming trip.
That's My 2cnts.