I have 15 trees planted this year, and rather than spending 2 hours
travelling and 1 hour watering them every day or so, want to set up some
irrigation for them, I had initially thought of soaker hose but probably
some form of dripline would be better.

Does the pipe come with perforations at regular intervals, or do you
have to pierce it where you want? Is there a general standard or do
they all vary per manufacturer. Should you try to adjust it to a
low/constant rate or control it on a timer?