I have a very very timid 3 year old, and we went to all 3 parks.
IOA - we did the caroseussel first - this was great. Then we did Cat in the Hat - she was terrified - it gets very dark, spins quickly and flashes a strobe light, not what I was expecting.
She wouldn't do 1 fish 2 fish because after cat in the hat she was terrified of everything.
My dh & I did babyswap on Spiderman, and while I loved it, I wouldn't take a nervous child near it.
Me Ship Me Olive was great - she loved that.
Jurassic Park - this was not great - even the kids play area roared and was scary.
Circus McGurcus - this is in Suess Landing, and is a character meal which was excellent.
There is also a very wet play area in Suess Landing which was a big hit.
Universal - we did Barney for about 2 hours, which was superb.
we also took my dd onto HannaBarbara, and this really shook her up, she was in the stationary seats, and I had to bring her out as she was so upset.
We did babyswap on a few things, and they were super, they have a lovely a/c room to wait in, and it was very well organised.
We also say the Blues Brothers which she enjoyed, and we enjoyed the ambience of the place, we saw quite a few characters around and about. I think we preferred this park to IOA, even though I hadn't expected that.
MGM - We started with Muppets 3-D, and I really wasn't sure if she would like it, but she really enjoyed it. She also enjoyed Bear in the Big Blue house, didn't complain in Backstage Pass, and loved Who wants to be a Millionaire (we have watched it loads on the tv so she was very familiar with it.)
We also went to the Honey I shrunk the kids playground which was good. We had lunch in the 50's prime time, and I think it all went over her head.
sorry this is a bit long, but I thought it might help. Especially be wary of that Cat in the Hat ride, it is not an innocent kiddy ride. It took 2 trips around 'Its a small world' to get her confident enough to do anything after that.
Bev