How about Mauritius? May is a good time to go and it is malaria free? There are some great family resorts too.
Have you looked at the sensatori resorts (Thomson)? They are really lovely and have both family and adults only areas and seem to be designed for luxury. They have a few locations around the world. The brochures always look lovely. I went to Mexico on our honeymoon and when I was 14 (with my 4 yo sister) and we both had a great time. I wouldn't say that it's not for kids x