Well, the sleeping arrangements are not going to be the problem. But for four gals, the bathroom really is! You are going to have to schedule it!
The first two out of the bathroom need to get out to one of the public rooms while the second two get ready.
One big tip ... forget about showering in your cabin. The spa has big beautiful showers with big comfy towels in the changing rooms that are free. Work it out so your daily shower is up there!
Budget/good shore excursions makes a bit of compromise necessary. As you know Half Moon Cay is a place you can just enjoy without spending a lot of money.
Aruba is not, IMHO, all that thrilling. We did a tour to Hole in the Rock or whatever it is called, and the butterfly farm, OK but nothing exciting. The beaches looked wonderful if you want another beach day.
In Curacao I definitely recommend the Seaquarium! You can get a taxi there and it won't be all that expensive. I suggest splurging on the sea lion encounter, or the dolphin encounter.
You can check our trip report at
The Halls Southern Caribbean Cruise
Have a GREAT cruise!