The Formal Nights are a 'Black Tie' affair, Tux and the trimmings, but a dark suit and shirt and tie will do for the hubby. I'm sure you have a nice couple of frocks in the wardrobe you could take with you. Alternatively, you could utilise the services of www.cruiseformal.com
who will supply formal attire at a reasonabl'ish' cost and will be delivered to your stateroom.
The no tipping comment was low and unwarranted by the way.
Have a great cruise!
My first is on the 11th of this month from Barcelona.