I was at Coral World in July with a 6YO, 3YO and 20MO. I've you never been to St. Thomas, just know that there are Iguanas everywhere and especially at Coral World. This is no an issue for me, but some of the children in our group, including my 6YO were a bit scared by them as they are the size of a small dog.
We only did the park, not any of the extras, and 90 minutes was enough to see it. We went to the Butterfly gardens after that, which was also cool to see. If you go in expecting to be wowed at every corner, you will be disappointed. If you go hoping to see some neat sea life, maybe pet a stingray, or if you're doing some of the other excursions like the Snuba, you won't be disappointed.
I'm so sorry to hear that some posters had trouble with the staff, especially the one who had the encounter with the Sea Turtle. In my time there I noted the staff was generally very passive, but would step in and help if asked. They all appeared to be about High School or College Age (mostly girls) and friendly and polite, but not catering to every need certainly.