Oscar Gandarilla called his son out of school Thursday in Rawlins, Wyo., and the father-son duo made the trek south to Coors Field — all to hear snippets of a single song one last time. Yes, the 36-year-old Denver native wanted to get a final in-person glimpse of his favorite Rockies player, Charlie Blackmon — the bearded, hard-nosed, sweet-swinging left-hander who’s called Coors Field home for 14 seasons. But it was more than that as Blackmon, 38, was set to retire on Sunday.