I have a bag of buttons, dice, game pieces etc. that I use as people when blocking on my countertop at home. I find it extrememly helpful especially with big casts. The variety of pieces helps me remember who is who. (The dice have played the protagonists for for years.)   Blocking at home helps me make sure that I have accounted for every character's entrance, movements on stage and exit before I get to rehearsal. The pictures are cleaner and rehearsals go so much faster.

I think you will have to do some blocking ahead & some during the show.  Do you have the cast yet?  In our HS show, the blocking changed between two casts (show was double cast) because one of the actors was shorter, and another actor was totally hiding him by standing downstage of him.  Is it a large cast show?