Here's the official word on tipping at the official DVC Web site --
http://www.disneycruise.com/
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Help! I'm really confused about tipping
We'll make it easy. Of course, you should never feel that a reward is automatically expected from you. But it is customary to give gratuities in recognition of service, which you will most likely be treated to in abundance aboard the ship. As a guideline, may we suggest the following:
Per Guest per cruise 3-Night 4-Night 7-Night
Dining Room Server 11.00 14.75 25.75
Dining Room Asst. Server 8.00 10.75 18.75
Dining Room Head Server 2.75 3.75 6.50
Stateroom Host/Hostess 10.75 14.50 25.25
Dining Manager Your Discretion
Room Service Your Discretion
For your convenience, a 15% gratuity is automatically added to bar, beverage, wine, and deck service tabs. All gratuities can be charged to your room charge. At the Walt Disney World® Resort, 15% is the customary gratuity at restaurants and bars.
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The table above is person (adults and children), per cruise (not per day).
It's important to tip the server, asst. server, head server, and stateroom host because they essentially depend on tips for their entire income beyond room, board, and a token wage. People who haven't cruised before are often shocked when they total up the numbers. But by the end of the cruise, they're likely to tip more than the recommended amounts because of how hard they work and what great service they provide.
The tipping process is easy. You get four envelopes near the end of your cruise. You can charge the tips to your account at Guest Services; they give you tickets printed with your name and the crew member's name; you put them into the enveopes and present them on the last evening. (You can tip cash if you prefer.)
You don't leave any tips at breakfast or lunch. When you tip your dinner servers, you're indirectly tipping the breakfast and lunch servers too. That's because the servers who served you at the open seating breakfasts and lunches also work at dinner, where they receive tips from their dinner tables; those people are tipping for your breakfasts and lunches. And when you tip your dinner servers, you're also tipping them for serving breakfasts and lunches to other people. I'm not sure I explained that well, but I hope you get the idea.
Drinks are easy. They automatically add 15%. There's a line to increase the amount, which you may want to do if someone really went above and beyond for you. You may also want to tip more in Palo, where the standard gratuity charge seems too low in comparison with what you might tip for a similar multi-course dinner on land.
You really don't need to tip the non-tipped positions, such as the child care staff. But some folks here like to give them phone cards, retail store gift cards, or other gifts as an extra thank you.
The IRS is not an issue. You're on a foreign-registered ship with a foreign service staff. (That's why the ship doesn't have to pay U.S. minimum wages.)
My guess is that all tips are appreciated, whether paid with vouchers or in cash. The vouchers are probably easier for everyone because the money goes right into their account. I assume that the cash tip recipients would have to stand in line at a cashier to deposit any cash that they get. (I doubt they'd want to keep the actual cash in their shared crew quarters.)