That is fine for 1 device, how about 75 devices?

We are asset tracking company that use ICOM VHF\UHF with gps receivers attached or built-in to do the tracking.
The radios presently have voice and data on the same radio. I want to separate the data from the radio and just use the radio for UHF/VHF voice communications only.
I have been experimenting with a XBee GPS Receivers and XBee ProS3B modules and I am pleased with the range. I would probably want to use the modules in a mesh network.
Presently the gps receivers are streaming the gps data through the XBee router and a XBee Coordinator connected to the computer through a USB Port. Our software shows the position on a digital map. That is fine for 1 vehicle but we have applications for 75 vehicles. In my opinion streaming gps data to the computer will not work.
When we use radios the position is sent at intervals every so many minutes. This what I want to do with the gps receivers and the xbee modules. Also with the radios the string also includes an ID number. So we know which radio is sending the string. I would also need some form of ID Number to show which XBee sent the gps position. I think I have to use an Arduino programmeable controller to set the intervals in minutes for the gps receivers. Do you have any simpler suggestions?

Most GPS receivers have the ability to set an interval as to how often they send. Why are you not using this function?

As for knowing who sent the data, if the GPS does not include an Address function, then you can always use API mode on the Receiving XBee. That way the 64 bit address of who sent the data will be included in the frame.