OK, details re: resort ID's:
The resort ID (your hotel key card) has a magnetic strip on the back of it. That strip is coded with your guest info; name, address, phone #, room #, etc., and also with charge authorization if you have approved that. For the Disney-owned hotels, any cash register on property can scan that strip and get identification information off of it (mostly so that if there is a question about who you are, they can verify it.) The name of the guest who made the reservation for the party is also printed on the front of the card, along with the dates of stay. If you buy your passes at the hotel or have UPH's with a package, this card is also your park pass. If you don't want to have little children carrying their own park passes, I suspect that the resort will be willing to create an extra key-only card for your child to carry. Be sure to give them your cell phone instead of your home phone to put in the guest record. However, even if you don't carry a cell phone, once you report the child missing and give your name for the alert, any CM that has him can match him up with the name on the ID card.
Swan and Dolphin give out similar cards with name/date printed on it, but the CM's cannot just scan them to get the ID info., and calling the hotel desks to get it might not be easy, due to privacy concerns. I'm looking at one of their ID's right now from my last trip, and it does have a lot of white space on the back of it; we used a Sharpie marker to write the cell phone number on it.
(A Sharpie is a wonderful thing to have; I always carry one.)
We prefer to carry our park passes & resort ID's on lanyards in zipper pockets, so that they are handy for the fastpass machines, and so that I can see at a glance that I haven't left the pass in the machine, or that no one has forgotten theirs in the room. I get the little ID holders from Wal_Mart for $.97 each, and put each one on a really bright-colored shoelace with a little spring toggle clipping the ends. (They come w/ a black breakaway cord w/ velcro, but I prefer to switch to give each person a color.) If you pull hard on the cord, the toggle will come off, but it holds fine for normal wear and tear; this is a safety precaution on the chance DS tries to hang himself with it in a playground (not likely as I have him put it under his shirt before active play, but still it's a good idea to have the cord be a breakaway.) The clear pouch has two pockets, an inner zip pocket and an outer one; the inner one holds the ID (and for grownups, the park pass), the outer one holds any pending FP, which is quite handy, IMO.
In our room, we keep these lanyards on the robe hook on the back of the door, where we can keep track of them and distribute them every morning before going out. I've often considered making up a few dozen extras to sell at the bus stop; we get asked all the time where we bought them! (I wouldn't REALLY do that, of course, WDW frowns on guests soliciting.)
