My wife and I were just at the Sandals Grande last month for our honeymoon... We were there for a week. It was a great vacation. A few things to keep in mind... Don't plan on drinking much beer that week unless you like Red Stripe, because that's all they serve on the resort. I decided to turn in my man-card and drink a bunch of fruity frozen drinks. I highly recommend the Jamaica Smile, it's equal parts strawberry daq, pina colada, and is topped off with rum cream. They don't have much booze in them, so I bet I drank 15-20 of them each day we were there haha. Also, make sure you take a pair of closed-toe shoes, I only took flip flops and brown leather sandals and several of the restaurants there require men to have closed-toe shoes and long pants. So I ended up having to go into town to buy shoes. I would also recommend taking the shuttle bus over to the Sandals Dunn's River resort for dinner a time or two. There are two really great restaurants over there... There is a Japanese steak house over there that requires reservations, and it fills up several days in advance, so I'd recommend setting up a reservation as soon as you check in. The other nice restaurant over there (i can't think of the name of it) served up an EXCELLENT filet... I had steak at 3 of the restaurants (not counting the Japanese steak house) and the filet I got at that place was the only good steak. The other two places I had steak didn't know how to prepare something medium-rare, they both came out well done.
We did two off-site excursions. We did the Chukka Zip-Line Canopy Tour which was incredible, highly recommended. We also did the Bob Marley party cruise which was a lot of fun as well... The party cruise sails out on their 70 foot catamaran, stops over a shallow-water reef for snorkeling, and then takes you to Dunn's River Falls... Even though you said you don't like tourist traps, I would highly recommend the Falls. Then you sail back to the resort and they open up the bar on the boat and everyone gets drunk. We saw the boat come back in a couple times and they were having to carry people off they were so drunk. Ours didn't get that wild because on the way back there were 6-8 foot swells so it was almost impossible to hold on to a drink without spilling or having it filled up with sea water.
The only downer for our trip was when we went to check out and pay for our incidentals, the guy was like "why didn't you use your spa credit?" and we were like, "what spa credit?". Apparently we had a $250 spa credit that was included as a perk when we booked online, but we didn't know about it. And of course they didn't bother to tell us about it when we checked in. So that really put us in a foul mood, especially since they wouldn't let us use the credit to pay for our incidentals or allow us to transfer it to our next visit.