Good morning Alice,
Don't bother to pack a hair dryer unless you have long, thick hair. Every room on the Grand has a built-in hair dryer, but they don't have much power. I have short hair, so the dryer worked well for me.
A travel iron isn't needed, either. Most of the decks have a laundry room. Ironing boards and irons are available there free of charge.
We packed pretty light. Most of the time I wore a bathing suit and cover up, shorts, or capri pants T-shirts and sandles. We tended to dress up for dinner, only because we like to do that. For dinner John typically wore slacks, shirt, tie and a blazer; I wore dress slacks and a blouse with blazer, or a dress.
You won't have to dress up in the ports. A bathing suite and cover up is all that's necessary at Princess Cays. Shorts or casual slacks and a T-shirt are fine everywhere else.
If you go to the Mayan ruins, wear sturdy sneakers or walking shoes. The ground is uneven and rocky.
Pack water shoes. The beaches and water tend to be stewn with rocks and coral.
We enjoyed the "anytime" dining option. For us, the freedom to choose when we wanted to eat and with whom, if anyone, was what mattered most. We didn't miss having the same waiter every night. In fact, we enjoyed meeting new ones! We rarely had a wait for a table for 2. One night we waited 20 minutes, but the time went by quickly.
John wore a black suit, white dress shirt and dark tie on formal night. I wore black velvet slacks, a red glittery top, and black velvet sandles.
Have a wonderful trip!