You could also hook up a quick-disconnect fitting like this one:
http://www.hydraulic-supply.com/imagesorg/aqpfd41.jpg
Instead of having a manual valve at the point the compressor attaches.
It solves your problem of accidentally trying to charge only a 6" section of tubing, instead of the whole system.
It's also designed to be connected and disconnected many times, whereas the standard kind of tubing fittings used in FRC are really not meant to be used that way (Though they do hold pretty up well under that sort of use).
You can put the male connectors on each pneumatic system, and just one male connector on the hose/tubing coming from your compressor.
Another bonus: These can often be found at local hardware stores, they'll probably be with the air tools (Nail guns and the like).
As far as I know, these connectors are legal for FRC use (Though as you said this is an off-season project, that may not matter).
As others have said, you do need to have a pressure relief valve on the compressor. It's not just the rules; it's so that you don't blow anything up
