I, honestly, would be careful letting 2 kids this age (boys or girls) go out too late without a "local chaperon". Usually you will end up meeting a staff member at the hotel or other resident that will show themselves to be trustworthy and willing to handle this responsibility. If someone offers to be a chaperon, I generally rule them out. I usually ask the person I feel is most responsible. Even with other young people (early 20's) that don't "belong" to me, I have given the trusted friend or employee money for the cost of admission and a couple of drinks to go with and keep and eye out for the inexperienced visitors. You definitely notice the difference if you walk the beach at night with just other tourists vs. if you walk with someone local. Maybe not a necessity, but just a measure of comfort.