If you haven't already, read our verified reviews and ship tips for Nieuw Amsterdam here: http://cruiseline.com/ship/nieuw-amsterdam
Holland America does tend to attract a slightly older clientele than some other lines, but the exact passenger mix will vary depending on the length of the cruise, itinerary and time of year. Seven nights in the Caribbean in February should be a good passenger mix, and you'll find plenty of entertainment options. However, you may find the nightlife a bit more subdued than some of the other lines. If you're looking for all night dancing in the disco or a "party" vibe, you'd do well to consider some other options, but if you just want the opportunity to dance and enjoy some good entertainment, you'll likely enjoy the Nieuw Amsterdam.
Let us know what you decide!