Try San Andres Island. It is a nice Colombian Island off the coast of Nicaragua. Not dangerous. 7 shades of blue/green water. I love the place. See the link below.

You did not say where you live or how long you would like to be away. $2k-$4k will take you just about anywhere you would like to go.

Florida is lovely and inexpensive, Orlando has lots to do and cocoa beach is only an hour as is clearwater.

California Also, Las Angeles has amusement parks, hotels Restaraunts and Lots of beaches.

Mexico is reasonable also. Cancun has world class hotels and pristine beaches.

You could take a cruise on just about anu cruise line and probably have lots of money left over. With a cruise all of your on board activities and meals will be included in the cruise price. You will also enjoy visiting many beaches and island on one vacation.

With your budget I am sure you will be able to go somewhere very nice and have a lovely trip.