G.,
We took our daughter for the first time in May. She was 20 months old and she loved it. We only went to Disney (Magic Kingdom) for one day and we easily filled the day. We did the Fast Pass for all of the rides it was available for and it worked really well for us. Our daughter liked most of the rides we took her on and loved It's a Small World. We did rides like Dumbo, Alladin, Peter Pan, Snow White, Winnie the Pooh, etc. My daughter did not like the 3-D movie at all (Mickey's Musical something or other), she cried during most of it. It has come highly recommended, but did not work out well for us.
They have really good food for kids at the park and I was really pleasantly surprised with the options.
We didn't stay on site. We stayed at a Residence Inn that was very close. Parking at the park is really cheap and I liked having a suite with a separate bedroom and a kitchen. My husband's parents joined us so we got a 2 bedroom suite for a very good price and the drive to the park was no more than 10 minutes.
Book early for a meal with the characters if you think your child would like that, they fill up quickly. We got reservations at the Rainforest Cafe for the evening that we arrived in Orlando. We had 5:30 reservations, I think. It worked out perfect for us. You go through security for Animal Kingdom to get to the restaurant, but you don't go into the park. As we were going through security the woman told me that they were lining up to see the characters. We got in line to see Minnie and we were perhaps the 6th family in line. So we waited maybe 10 minutes and my daughter got to get her picture taken with Minnie Mouse before we even had to go into a park! That took a lot of stress off me. Minnie is my daughters favorite. The pictures turned out really well because my daughter wasn't sick of waiting in line by the time we got to see Minnie. We easily could have gotten in line to see Mickey as well but decided not to press our luck and went to dinner.
Good luck. I am sure you will have a great time with your daughter.
D.