Honey moon ideas !! Help???


So my brother brakes the news to me that he wants me to plan there honeymoon, as far as she knows 'they cant aford to go' but hes actually passed me £4,000 to plan them a special 2 week trip.. Hes saved up for this for the past 3 years , he said he doesnt want to know where there off to until the day .. Im scared of not being able to plan a romantic 2 weeks for them.. I dont even know where they could go so im here asking anyone who has any ideas on where to go or what hotels they recommend ?..

His wishes are :-

The place has to be authentic and tropical , plenty of wildlife / small beaches and local foods.

I was thinking of costa rica but ive herd theres a lot of rain fall there so just want to hear what others did for there honey moon?

There getting married the 24th of july and wont be leaving until 25th or 26th??