My main problem is that every tutorial and example of XBee temp networking I can find, and there are many, configures the XBees in API mode. I assume this is because Rob Faludi used a temp network to demo API mode in his excellent "Building Wireless Sensor Networks" book.
No, it is because in API mode, the "who sent 14.7" bit is dealt with.
You could make each Arduino send data differently ("<1:14.7>", "<2:14.8>", etc.). Then, on the coordinator, parse the data and determine who sent it.
But API mode is not only beyond my abilities of comprehension at this moment, it also appears to be something of an overkill for a project which, for the time being consists of relatively simple communications.
The XBee library makes it pretty simple.