I cannot answerer your questions, but let me give you something to think about.
Our first cruise, two summers ago, we bought very nice walkie talkies, because we were told we would need them on the cruise to keep up with the boys. We used them one half a day. Parts of the ships block transmission. So many kids on the channels, it was hard to tell who's kid was who's. They were a pain to keep up with (the W.T)
Sailed the Sensation April 12-15, 2007. We had a good experience with walkie-talkies. We bought 2 decent sets by Cobra (6 kids to track) at Wal Mart for 18.99/set and we used them a lot! The ones we bought had privacy settings that enabled us to have a channel no one else was using. We were on the Upper (3rd) deck and were able to contact the kids no matter where they were. Other than while swimming, the kids just kept the walkies clipped on their waists.
I don't know about rentals on the ship but I always take and use mine. Sometimes DW and I cruise with the adult kids and our grandkids they come in very handy. I use Midlands and Cobras. We also use the privacy settings and alert codes so we know who is calling who. I think most ships do have "dead spots" but the majority of the time we have no trouble getting out. One thing I do notice , not all cruisers are happy with those of us that use the walkie-talkies, they say we are a nuisance. That's fine I still take and use mine.
Quantum of the Seas 12/2014
Oasis OTS 6/2015
Serenade OTS 12/2015
I've never heard of rentals, but that doesn't mean it doesn't exist. On our first cruise, we had a 12 & 15 year old and no walkie-talkies. After that, we had walkie talkies! We bought a couple of sets....and we've used theme at Disney World, AstroWorld (when it was open) and on other family trips.....you can just call me Mama Bear!
If you are going to walk on thin ice, you may as well dance!
We used them when we cruised with our sons. There were lots of kids and adults on the many channels but we came up with code names to identify who was who and we instructed the boys not to give out their cabin # or info over the radio. They did come in handy. DH and I just use post-it notes if we go separate places.
Teresa and Larry
#36-Carnival Splendor 9/16/12
7 night Mexican Riviera
#37-Allure of the Seas 11/11/12
7 night Eastern Caribbean