We were just recently on board Explorer and yes you tip the last nite out, the cabin attendant will leave the envelopes for you. For the Cabin attendant and your waiter is $3.50 PP per day and the assistant waiter is $2.00PP per day. You may also want to tip the head waiter $10 or so depending on what he actually does for you, we did have a very good one on Explorer and he deserved some cash as well.
When we cruised with our kids we always tipped the same for them, in some cases they are even more work for the waiter and cabin attendant. Many go out of their way to make the cruise enjoyable for kids so they do earn their tips, the same as with us adults :-)
Have a great time on Explorer, in case you want to read my review:
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