We stayed at the WM Fiji a few years ago for 10 days. We had a great time. This was followed up with an 11 day stay in Rororua, NZ. While the Resort is on the Water it is not a swimming Beach. If you visit the Hindu Temple remember they are a Modest Religion. Honor it. Patti wore a blouse with a high neckline with sleeves to her wrists and a skirt to her ankles. I wore a long sleeve shirt and trousers to my ankles. We were the only folks in the tour group that were not required to wrap ourselves in Robes. To get the best snorkeling or diving you need to travel off Island. There are many day trips to snorkeling areas.
We flew Fiji Air from LA to Fiji and then Auckland, NZ. They also leave from San Francisco. We have also flown Fiji Air to Sydney and Melbourne, Australia with just a couple hour layover over. Last Winter we were flying to Melbourne. Fiji Air was $100's less than Qantas or anyone else. As we got closer to departure Fiji Air offered us te opportunity to Bid for a Business Class Seat or pay a little more and be guaranteed an empty seat next to us. Patti ended up with a 3 Seat Row to herself and could lay down. Fiji Air is a top rated Airline.
If you set it up in advance you buy a ticket from the West Coast to Auckland (or various locations in the South Pacific) with a week or more stop over in Fiji. Then continue on to your other location.
Remember if you leave the West Coast on a Friday you arrive in Fiji on a Sunday. International Date Line. But you arrive very early in the morning. But checkin is not until 4pm so you should have your Reservation actually starting the day before you arrive so when you get to the Resort early in the morning you can checkin right away. Also you need to have your Reservation run 1 day long. Most flights leave Fiji for the USA very late at night but checkout time is 10 or 11 am. So if your Reservation runs through the day after your Departure you do not need to checkout until it is time to travel to the Airport. You will arrive on the West Coast early in the morning. Before normal checkin.
It appears you will be traveling from the East Coast. You should plan a day or two stopover in LA or San Francisco each way. Fiji Air also has uses Dallas/Fort Worth.