Have been at all four and stayed at Nevis and CR. Have to agree with aa213bb that the Maui FS also seemed to me to be plopped/wedged into a beach area and not all that appealing to me. But did not stay there. Also did not stay at Haulalai but the property but was there while on the island and is beautiful and not at all like Maui. Gets incredible reviews and many just love it. Seems to have lots for kids.

Nevis FS is beautiful and although I might agree that it is a bit of an anomaly on that island, they do a good job of being elegantly low key enough and it is easy to get into town and blend into the local surroundings. We loved our time there and the fact that the property fit with the area. Local fish shack down the beach that blared opera etc. Nice spot but quiet and not a lot of action. Probably not a lot for the younger crowd unless things have changed.

FS CR is quite isolated by car due to the peninsula, but there is a 20 min ferry (if memory serves) to a town near by. Rooms are gorgeous and the porches are even more incredible. Washer/dryers on every floor (a big plus with kids). It has been a while but I seem to remember lots to do there for kids and adults. We also did this after exploring CR and ending up there. The only downside for us is that you are more than a bit "trapped" for eating there which fine, but not much opportunity to break for the local culture and less "restaurant" style food. But a beautiful place.

If it were me I would pick FS CR or Haulalai for your family situation and would depend entirely on whether you wanted to explore Hawaii or Costa Rica. I suspect the resorts for families are quite analogously suitable and lovely.