I worked for Princess Cruise lines as a musician for years, (not long ago) and I've been on dozens of cruises as a passenger on Princess and other cruise lines. We (musician/employees AND passengers) were ALWAYS bringing crazy things on the ship - many of which were "not allowed". Just be smart (and nice) about it. Have a story prepared.
Although their policy is "no drones", I would take my Tello, maybe not the Mavic. Keep it on your person, in a carry-on bag / camera bag. IF the ship security running the X-ray scanner when you're boarding says anything about it, I'd say,
"It's just my toy-flying-camera. I know I can't fly it on the ship, but I want to take pictures with it in the ports."
If they still say "They're not allowed on board", then say,
"Okay. Where can they hold it for me while I'm onboard, so I can pick it up when we stop at the ports and use it on shore?" -- They will probably go for this.
If they STILL say "That's not allowed", then say,
"Okay. Tell we who I need to retrieve it from at the end of my cruise." - They will definitely hold it for you until the end of your cruise.
I'd bet that if you just had a Tello neatly folded up in your camera bag, there's a 80% chance they won't even identify it as a drone and won't say a word about it. They are LOOKING for drugs, alcohol, and explosives. Most of them associate a DRONE with the PHANTOM, or similar large device with lots of big propellers.
They WILL NOT: destroy it, confiscate it forever, make you pay a fine, or kick you off the cruise. Cruise security personnel are not in the business of irritating or disappointing passengers. They are specifically trained to try to keep the passengers happy at all costs with two exceptions: 1) does it pose any real safety risk to passengers or the ship 2) would it possibly mean costing the cruise company any money, or inhibit their ability to MAKE money. (i.e. - bringing your own alcohol) They know you have many options as far as cruise lines, and they make a huge % of their revenue from returning cruisers. They REALLY want you to come cruise with them again and again, so they really want to work with you.
Of course it depends on the individual you're working with, everyone is different. Most people respond well to politeness, respect, and honesty. Worst case scenario is that you won't see your Tello again until you disembark for good.
Personally, I'll probably take my Mavic on my next cruise, for all the above reasons. But I'm pretty comfortable chatting it up with security guys, and I do trust that no damage will come to the drone even if they do end up confiscating it for my entire trip.
I wouldn't want to be in a bunch of beautiful, scenic places with NO drone and spend the whole time thinking, "I should've at least tried."
Just my 2 cents - hope this helps.