I notice that the first two replies referred to the $5 per person charge as a "cover" charge. It's not a cover charge; it's an automatic gratuity charge. According to
DCL's official
Fun Onboard Q&A page:
<DL><DD>
Is there a romantic restaurant just for adults?
The ship features an adults-only alternative restaurant called Palo. Dining hours
for Palo are 6 - 11 p.m. Reservations are required, and taken (once on board)
on a first-come first-served basis. Palo dining is limited to Guests 18 and older.
There is a service charge of $5 per Guest for gratuities.</DD></DL>
So, for a couple, that's an automatic $10 tip. If the food is worth $66 per couple, that equivalent to a 15% tip. (I'm only counting the food because there's an automatic 15% tip on any alcohol or fancy beverages.)
But a similar multi-course meal would cost more than $66 per couple at most US restaurants that are comparable to Palo. And the excellent service would deserve more than 15%.
Let's suppose the dinner is worth $80 per couple, and you want to tip 25%. Or let's assume the food is worth $100 and you want to tip 20%. In either case, and extra $10 will do it.
There's blank line on the receipt where you have an opportunity to increase the tip. If a couple adds another $10 in addition to the automatic $10, that's a $20 tip, plus the automatic tips on the drinks and wine. That seems like a good tip.
I think that adding $25 to $40 per couple is extremely generous. Of course, that's fine. I'm sure the servers are thrilled. But I don't think that's common or expected.