One generator, 2 transfer switches is the way to go. We have used 3 or 4 switches with one genset before. With multiple switches if something happens to the utility service lateral(drop) on one building it can start the genset and be powered that way, without powering all buildings. The transfer switch start wires are connected in paralell so any switch can start the genset, but power has to be restored to all of them before the genset will shut down. Never had any problems doing it this way, but I am not in Canada. just my 2 cents.
