I will also add your intention to make the 15 mile trek to the irrigation supplier will pay dividends back in the assistance you will get (in theory - depends on the staff there
)
One more thing - aside from possibly a filter - depending on your water source - you do not need any other bells and whistles. Just the tubing , maybe a few couplings, and the (round topped) staples. They make a wide variety of drip tube accessories but just for a line of trees you won't need them. You'll also need a way to plumb it to your water source. Maybe get a drip tubing 1/2" male adapter & threaded coupler that converts FPT to FHT (female pipe thread to female hose thread).
Then you can screw the drip tubing to the hose that goes between your timer and drip tubing. I hope that makes sense.