Here is what happened to us last year:
When we got to our resort (AKL), we asked at the desk if there was anything that might happen if a kid lost a tooth at WDW, as our older DD was about to have one go. The CM suggested that we should tell our DD that Tooth Fairy duties were covered on WDW property by Tinkerbell (fairy union rules, I presume), and they could get us some props when and if the time came.
When my DD lost a tooth on IASW (now that's a Disney fan), we got off the boat and my wife ran to the nearest store to get a box in which to stash said tooth. The CM behind the counter was awesome and made a big production complete with painstaking wrapping and "pixie dust" glitter and generally making a fuss.
We made sure that we took good care of the box, got back to AKL, and did some flanking maneuvers to get one of us parent-type people to the front desk to see if we could follow through on whatever the first CM had planned. My wife tracked said CM down, and that CM got her one of the light-up Tinkerbell things that they put in some of the kids' drinks to add to the presentation of the tooth ransom.
It worked out really well, and I think let the CMs have a little fun with what was a pretty big deal for DD at the time.
Incidentally, same DD lost a tooth the day after we got back from this year's WDW vacation.