There is no-thing to do on Bintan Resorts, the posh bit you are presumably going to do. There are some more things to do on the rest of the island, although many are dangerous to your health in more ways than one.
But if you really want to just relax, then yes, Bintan should be just fine. Banyan Tree is quite expensive though and more a place for couples getting it on than a rowdy bunch of friends...
More info:
http://wikitravel.org/en/Bintan