We've done a Halloween (& more than a few Merrytime (Christmas season)) cruises as well as 'plain' cruises

. You can trick-or-treat if you like, but the kids get first shot (naturally). The atrium is PACKED, but lots of fun. DW & I dressed up (Bride of Frankenstein & the Monster) while DD 1 & 2 were the 'Frankettes'. DS was going to be Frank Jr, but came down with a case of teenager-it is.
What's fantastic about
DCL is that you can choose to make it as frenetic as you want. We've done some cruises where we're nearly running from event to event and others where DW & I grabbed a cuddle pod outside the Cove Café and whiled an afternoon away chatting and sipping some really good joe. Both have been fun' it really just depended on what we needed. In 21 days (yeah, counting down!) we're doing a 3 day and treating it as a long weekend getaway. Next summer, we're doing an 11 night Southern Caribbean while in between we're doing a 7 night Alaskan cruise.
We too did a short cruise at first to see if DW was into the 'seagoing vacation'. I'm a former Naval Officer, so I knew I'd love it and after our first full day the entire family was in love with DCL.
Beware, it's addictive!