We are going on our fourth
Disney cruise but first 4-night next summer to the Bahamas on the Dream as well; we've only done 8 and 7 nights, so you are right, 4 nights is short for some people! But others think it is a great introduction to Disney cruising. If you go on
Disney Cruise Line Blog, you will, as others have mentioned, find the Personal Navigators, which you will receive each morning (and when you board). i would highly recommend finding your exact itinerary and mapping out your day. Here's one with the Nassau day:
http://disneycruiselineblog.com/wp-content/uploads/2016/06/Personal-Navigators-Dream-4N-Bahamian-Day-2-Nassau-20160607.pdf We also are not going to get off in Nassau (except maybe to walk around a bit). I think you will still be able to see movies then instead of other times and there are a few crafts and character meets. Maybe your kids will love the kids clubs; mine do. With such a short amount of time, we are going to try to just enjoy the ship. Also try to get the earliest Port Arrival Time that you can, pack a day bag (your luggage may not come to your room for several hours), and try to enjoy the ship as long as you can the first day as well. You can have lunch when you board and swim, do the Aquaduck, etc. That's our plan as well! Have the best time!!