Diving is Fiji is fabulous.
I'm biased because I had my introductory dive there, gained my Open Water certification a year later on Tokoriki Island and have dived there on every visit since. The highlight of the dive was hand-feeding moray eels with Castaway's dive managers, Craig and Karen Flannery. Craig and Karen run a very tight, but friendly ship. The diving on Castaway is very family oriented. If Mum and Dad want to dive, the kids can go out in the dive boat and swim and snorkel under supervision.