If the schools are local to you, there's nothing wrong with letting them know about your son before the Junior baseball season starts, assuming your son is on Varsity. We have numerous coaches and RC's come by to catch a few games. In general, though, the research and scouting is done during the summer just before senior year, with the whole commitment kerfuffle happening before the ED date.
There is definitely some recruiting being done after that. There's always some schools who were left at the altar during ED.