Q: once subscribed, does the main computer with library always need to be on in order for other devices to work?

I am trying to figure out if iMatch is right for my family.  We have 2 iPhones, 2 iPads, an iPod Touch, and a few PCs.  One PC has our music library on it in iTunes.  We want to all share from the library with our own separate devices.  If we subscribe to iMatch, does everyone need to use the same ID to access the library? Does the main PC with library need to remain on constantly for other devices to gain access? And my daughter has the iPod and we would like to control the content she is able to access, is this possible with iMatch?  Thanks