what do you know about these places in fiji?

l am going to fiji in May with one or two friends. We are going on the blue lagoon 3 night cruise. ( anyone been on this and got anything you can tell me about it?) looking at staying at treasure island and thinking about castaway or malono island. We are looking for somewhere nice,with nice white beaches and with the choice of either things to or relax what ever we feel like on the day.would like a little something to do at night for light entertainment. In our 40's and not into big night life stuff but doesn't sound like we get that in Fiji anyway.Would 3 nights be enough on each Island?

3 night blue Lagoon cruise was good but it was fairly rough when we did it.
Have stayed at Treasure and it was fine, Castaway and Malolo Island Resorts look good and 3 nights each would be ok at all 3.
Just back yesterday from 13 nights at Amunuca and go back next weekend for 7 nights at Plantation. we really enjoy the Mamunucas and they are all different.
Tried to book at both Castaway and Malolo for last two weeks trip but the travel agent could not get it together so we will do both of them later this year.
There is also Funky Fish on Malolo which we enjoyed as well as Walu Bay and LikuLiku Resorts which we have not yet been to but they look OK.

Castaway very pretty and quiet - great snorkelling - Plantation always something to do although not as luxurious as Castaway - the staff and good fun keeps us coming back to Plantation - I usually go with 8 girlfriends - we love Fiji

Just came back from 6 days at Castaway and had a great time. Was there with my 8 year old. We went snorkeling and kayaked around the island. Food was good, sometimes great (did the meal plan). Bure on the beach front was lovely. Took the Bush Walk up to the top of the island for great views. Pool is nice and covered; however, there are lots of kids around. Staff was friendly.