You won't be able to cruise with a family of 5 on 160 points. Not all of you, anyway. Maybe 2-3 of you on points, paying cash for the rest. And that would only be for the shortest, most inexpensive cruise, at the cheapest time of year, in an inside cabin.
For instance, for the 3-night Bahamas cruise, in January or early February, for the cheapest category of cabin, you're looking at 55-58 points per person. For that cruise, points go up to 116 per person, depending on what time of year you go and what kind of cabin you book.
For a 7-day Western Caribbean cruise, you're looking at 134-398 points per person.
Other important things to remember about cruising on
DVC points:
Availability can be sharply limited -
DCL only makes a certain number of cabins available on points. I checked availability in Sept 2011 and was told that nothing at all was available on any ship until Oct 2012.
Point costs are NOT fixed, and can and do go up every year. At some point, you'll likely find that you no longer have enough points to cruise at all without adding on.