Traveling with family (2 adults + 3 kids) from USA. We had a great time there. Kids absolutely the pools/beach/soccer field/the grill/pizza restaurant by the pool. Very quiet, peaceful and beautiful. We have been to Tahiti before and found this Marriott Momi Bay is even more relaxing, romantic, and picturesque than Tahiti. But there are also some pros: 1) the location is in the middle of nowhere (though no so far from Nadi). So once you are there, you will be pretty much stuck there; 2) food at the main restaurant is just average. They have an Asian food section for breakfast/dinner buffet, but quite a joke (to our standards, as Chinese Americans). The fish bar is awesome but requires a bit of walking/buggy ride; 3) snorkeling wise, the fish is not as colorful as in Tahiti, but is still very good; and 4) the layout of our room (2 beds by the pond) is not so much different from an upscale city business hotel.
Overall, if you are just looking for a relaxing time in a resort, this would absolutely be great place. But if you are looking for a new cultural/food/city adventure, this would not be the right place.