The cruise points charts list the cat 4 "family suites" I believe I heard that cat 3 (not sure 2 or 1) is possible but you have to call (but only if you are sitting down, preparing for the shock of the amount of points needed )
From what I've read, It may be tough to get a cat 3 as usually the better suites are booked very far in advance..
Yes, you can use points for the suites on DCL ships. They do not publish the points charts though. You'll have to call MS to get them. As hakepb said, they are VERY pricey and are often booked up far in advance. DCL accepts fax requests for suite accommodations so sometimes they are completely filled before bookings actually open up to the public...especially the very limited Cat. 1s and 2s.