The only reason we pH adjust our waters is so that our expensive EDTA chelated nutes break out of their chemical bonds and become available to the plant. If it were not for us using these types of artificial nutrients, we would never have to adjust pH at all, unless we were dealing with water outside of the normal ranges that supports life.
In your coots mix, there is no need to adjust pH. None. Anything you add to do so, will kill off a few microbes. It is not only not necessary, it is shooting yourself in the foot. In those large pots, it should be a breeze to keep things going... I suspect you are over thinking this.
Yes, There are two main branches of organic soils... for the coastal dwellers, coots has become popular... for landlubers, Subcool's mix is easier to get hold of the components. They are both good recipes to do what we do.