I don't see what the big deal with Atlantis is.. I wasn't that impressed when we were there, it's nothing more than an overpriced Vegas hotel. I'd rather stay at the Bellagio than Atlantis.
And whoever said the Don Cesar.. nice place. I've walked through it but we stayed at the TradeWinds which is a few hotels down.
If I were to go to Sandals, I would def pick the Grande St. Lucia or the Grande Anitgua resort.
A cruise is a good idea too, it will give you the opportunity to visit all the smaller Caribbean island (st. thomas, st lucia, st marteen, etc).