If money is no object, The Cliff is meant to be a lovely experience. Bit out of my price range, but my sister's been and very much enjoyed it.
The other restaurant I've heard good things about is The Tides and I believe it's a fair bit cheaper.
Places to visit - well Harrison Caves is the big attraction and it's recently been revamped.
A day at the races at Garrison Savanah is meant to be good fun. We meant to do it on our last visit but a huge downpour curtailed that.
The Atlantis submarine is a good experience and we also enjoyed the wildlife park. Other than that there's the usual Caribbean island sailing/snorkelling and helicopter trips. You can also do day trips to the Grenadines, but they're quite pricey.