I believe on the 4-night, you will repeat your restaurant on nights 2 and 3, so I would pick one of those in most cases to schedule Palo. However, keep in mind that you can STILL go to the dining room for an appetizer and a drink, if you have Main Seating and schedule Palo later on. (if you find out the approximate time for sunset around then, that's even better, so you can eat at Palo as the sun is setting - very pretty) Beware - there's a lot of food at Palo, so don't overdo it.
But this especially works out well if you have kids, so you can eat with them, take them to the clubs, and then head for your evening out. If you choose to eat at Palo on pirate night, you'll probably miss the pirate menu, and some of the festivities. So that might be important to you if it's your first
DCL cruise. I usually take a quick look at each dining menu and pick the one I like least, and then request a dining rotation and Palo Dinner from that.
Even without overthinking the Palo / dining rotation choice, you're going to have an amazing time. If you miss a menu you wanted to try, hey - there's always another cruise to plan for! You will not have time to experience a lot of things on a 4-night cruise, but that's OK. You'll be much more relaxed if you don't try to do it all, and save some treats for a future cruise.
Cabanas are fabulous, but people have also reported that they've had just as good a time without one. However, we always enjoy ours very much, and would not do without one unless we were doing a double-dip (special itinerary with two days at
Castaway Cay). Happy sailing, and enjoy concierge on the Dream - it is wonderful!