I don't know how much they are, but i went there a few years ago, and their PADI open water courses are recognised worldwide. my family and i did the theory in england, and learnt how to dive etc etc (albeit in a swimming pool!) , and we did our open water part of the course in the maldives. so all we had to do there were a few dives and prove we could do the exercises etc. And after that we could do the dives. So if you haven't learnt to dive yet, I would suggest that.
not sure what you mean by trips in the maldives, but i've been twice and both times there were island hopping trips, where you visit a few different islands in the area. some are inhabited, some aren't, you can spend a little time snorkelling off the beach etc. but apart from that, there aren't that many trips. there are usually a good range of water sports on the islands, so that should keep you occupied! Oh and also you can do more PADI 'courses' there, where you get add-ons to your PADI certificate...things like deep dives, night dives, wreck dives etc. it depends on where you're staying i suppose as to whether you can do all that.
You'll have a great time there, i'm very jealous!