My family does Dive Quest every year, it is a truly awesome experience. I hope you love it.
The entire tour takes about 3hrs. The 1st 45min start with a backstage tour, paperwork and getting all of your gear on. You can start to watch the divers around 6:30.
You will have about 40-45min of dive time.
There are lots of places to watch the divers in the aquarium, right against the glass. The problem with coral reef is there are very few tables that are right by the aquarium. Much better views are to be had in the aquarium. You can come right up to the glass and the videographer will take a video of you and your family. The video is extra, but worth it.
Just my opinion, but we think the Coral Reef is one of the worst restaurants we have ever ate at, in or out of Disney. Our food was terrible, small portions and chewy/rubbery shrimp, yuck! We also had terrible service, rude server and very slow. We were so excited to eat there, but it was an awful experience.