I will speak from my viewpoint as a fellow coach.
The triad is a classic physical structure because of its stability and practically. We also notice that this predilection toward triads extends beyond physical structures. Traditional families consist of mother, father, child. The self is thought of as body, mind, spirit. In reality there appears to be past, present, and future.
In coaching, typically we assist people in dealing with what there is to deal with from the past, so that they have a present, in which they are happy, and a potential future that lights them up, calls to them, and pulls them forward into its manifestation. Once these three pillars are in place, the coaching has done its job. The client will figure out a "how," once they have a big enough "why."
What I have found effective in my coaching is to help the client become aware that they are carrying the past with them (to the extent that they are) and to distinguish what this is providing for them; then what it is costing. (Not that any of it is good/bad, right/wrong; we're just looking for costs and benefits. Once people get that something is costing far more than it provides, giving it up becomes easy. It becomes something we do because we want to. It is exceedingly difficult to get someone to stop doing something they truly desire to continue.
Once again, I assist clients in dealing with the past, which leads to a present they are happy with, and a future which lights them up: past, present, future. You will also notice that my symbol consists of three nested triangles, a triad of triads, if you will. Each nested triangle spins off from its predecessor, just as circumstances and events spin off into others, and yet they all are interconnected and part of a continuum. That's life, and that is what I coach.
You may use this story in speaking of your coaching if you like. Of course it doesn't make nearly as much sense without the triangle symbol in your logo. ;o) By choosing my logo, you gain the alignment of my being, with your being, creating your practice and making a difference in the world. Once again, a triad. Ha!