Hi
Just back from the 4 day wonder cruise (28th April - 2 May)
We had a blast..!!
But to answer your question, 8.30 - 9.00 is about right but bear in mind if you are first seating at night you are supposed to take first seating at breakfast on debarkation day (6.30)
You are free to wander the ship and take final pictures etc, but you must be of the ship by 9.00 at the latest
Hope this helps