Barbados, St Lucia or Antigua - decisions, decisions...
You should have a good time on any of the above islands. We have stayed on Barbados and St Lucia and enjoyed them both (The Cliff is well worth a visit as has been mentioned).
'Fraid I disagree with Paul (p17blo), we really enjoyed St Lucia on the occasions we have been there, I guess this is partly because it was the first Caribbean island we ever visited (they say the first time is always special

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We have stayed at Sandals Halcyon and The Rendevous (both couples only so not much help with a family trip - sorry). We also visited a number of other resorts and hotels looking for new places to stay & eat on our next visit. We found the people generous and friendly, it is a poor island but they do try hard to make you feel welcome, IMHO.