Ahhhh. Tipping....
First, it doesn't matter who you booked it thru - it's almost always thru an independent tour operator that really doesn't have any ties to
DCL except a contract to provide this service - so yes, we tip. Second, yes, if we take a taxi, we negotiate the rate first, then we round it up & leave a tip just like we would at home.
On excursions, we generally leave about $5 from each of us (family of 3). If the excursion was a let down & the "crew" only so-so then we might leave only $10 - but likewise if it was a great time & the crew did their part to make it enjoyable we'll bump it up to $20 if they went out of their way. But I would say an average tip that we leave is $15. We might also consider the length of the excursion - a 4, 5 or 6 hour trip is obviously worth more than a 2 or 3 hour tour and a larger "crew" would have more sharing to do. But it's kinda like restaurant tipping - if you take a really long time for dinner & tie up the table all evening to the point where it can't be seated again for another tip, then you really should sorta leave more to compensate for the one they missed out on while you were plopped there. I figure on a 2 or 3 hour tour they'll probably have another one or two trips throughout the day - so they'll get more chances for tips whereas on a longer trip, that's probably their only one for the day... I take all of that into consideration - but I gotta go back to the average of $5 from ea. of us....