JAR - I admire you trying to nip this in the bud early and hope it works. I personally briefed all the coaches in one of my Rec leagues before the season, but didn't delve to deep into this issue as it hasn't been a problem.
My years with Rec league shows this to be a difficult issue as the experience of each individual ref will determine how this is enforced - and it probably won't be uniform.
I am one of the more experienced refs in our Rec league (that's not saying much
). I arrived at the gym Sat to watch some games before mine and had a ref tell me she T'd and tossed a 12U coach. I was shocked as I have never come close to Ting a coach let alone tossing one in this division. She said there was just too much "chirping." Her call. Some are quick with the trigger. Others, like me, try to tune em out it if we can.
Let us know how your process works as I might incorporate this in my talk next yr.