For the Maldives have you not got accomodation as part of a package ? - If not you'll certainly need to book somewhere.
I've never been, but I've always heard that the Maldives is not really somewhere for just turning up on spec to get accomodation. All the tourist hotels are on tiny islands (The maldives is a string of tiny islands) ... you arrive into the airport in Male and get transferred by boat or seaplane to the island where you stay for the 7/14 nights .. in many cases the only thing on the island you're staying on is your hotel ... you're essentially stuck there for the holiday ... you can checkout any time you like but you can never leave ... or something like that
I think a lot of the hotels there do most of their business with flight + hotel packages and are very expensive for independent booking (and are expensive for packages too!) ... You may well find that trailfinders have the best rates ... but shop around
The arrangement has always struck me as like a bit of a tropical luxury prison for 2 weeks with little possibility of escape

, hence i've never felt inclined to visit it myself having a low boredom threshold for beach holidays ( nice for a few days but it's nice to do other things too... and I dislike having to eat in hotel restaurants all the time) ... but many people I know have been there and had a great time - as with all travel it depends on what you like yourself .. it's likely a great place to relax after the big day.
For Sri Lanka, I'm afraid i've not got much advice... it's probably somewhere much better set up for travelling around
For Dubai - loads of posts here just do a search.