Yes, you can decide who gets charging privileges or not. We gave them to our 13-year old (with lots of warnings and rules) but not to our 10-year old. Can't recall the age at which
DCL allows you to give charging privileges, but pretty sure there is one.
I do not like wearing a lanyard and generally just keep my card/key in my pocket. As a general rule, you need the card to drop into a slot as you enter your room in order to turn on the lights, so I see it as a royal pain to have to pull the card out of a lanyard every time you enter the room. Several people buy or receive "light cards," which is basically a card with a magnetic strip on the back of it (I assume?) that tricks the system into thinking your card is in the slot....if you have that, then the lanyard wouldn't be as much trouble.
We did a "fish extender" group for the first time last week on the Fantasy, and one of the things we received was a card "slot" that stuck to the back of a cell phone. Our 13-year old daughter quickly claimed that so she could also stop dealing with a lanyard. With the next texting feature on the DCL app, along with the Navigator itself, she knew she'd always have her phone with her anyway, so why not just keep phone and card together?
There are DCL lanyards available in the gift shops on the ship, which serves not only to hold your room key but also is a little more substantial than the "
Castaway Club" (prior cruisers) lanyard, so you really could treat it like a little wallet around your neck....although the only "card" you really need on the ship is your room key unless or until you get off for an excursion, in which case you'd need photo ID and likely a credit card (and maybe an insurance card, cash, etc.).