i've heard that there are some really nice once is cancun, as mentioned above ...i'm not sure where you live or how far you want to travel - LOL - i KNOW there are some amazing places in bali, maldives, etc too - i haven't been able to go to any of those yet
we haven't done any couples only places yet - right now we always do club med b/c they have lots of kids activities
i would stay away from any of those (at least the ones that are family friendly) if you want something relaxing - haha - we went to club med punta cana in december and met a lady there who didn't realize it catered to families - she was really shocked at all the kids and noise! LOL!