For flights longer than 6 hours, fly separate from children and move to business class. In business class, get sleep. Alcohol may assist.
Everyone books spa treatment on "cruising day", so must need book ASAP before everyone else does. Seriously, try book even before going on ship. But this usually so popular, many ships not allow pre-book before get on ship. So, get on ship and book, even before going to room! Also, confirm and re-confirm spa treatment booking for this "cruising day".
After leaving and before returning to Civitavecchia, insist on knowing if ship will do Isola del Giglio salute. Give captain serious stern look so insist on truth. Of course, you not able to change plan either way, but can prepare accordingly.
Enjoy holiday,
Kuji out.