That's plenty of time to shop and explore the port of call. You may always return to the ship for meals or just to rest. On a cruise you can sample many destinations without ever packing and unpacking and spending valuable vacation time driving between new places. Every large cruise ship has a fully equipped medical suite and staff for any emergency. Most cruiselines have special childrens' programs for many different ages.
Cruises are a great way for families to travel.
There is something to do on a ship for everyone - and very safe to allow most children over age 6 to be on their own for short walks around the ship. Many new friendships are made on a cruise. A dark suit will suffice for any formal night on a ship. Tuxedos can allo be rented on many ships if desired, but they are not necessary. Tipping is up to the individual.