Greetings
Yes there is seating inside Terminal J. You choose your check-in time when you complete the on-line check-in which opens 21 days before sailing. Boarding usually begins around 11 AM with suites first to be called. Staterooms are ready later in the afternoon and will be announced on a deck by deck basis. You can have lunch, explore the ship, have a drink or four until the rooms are ready you just have to keep your carry-on with you.
Good Sailing
Tom