PA Systems can produce a huge volume - if you want them to.
As evidenced by many a ground delay (no pax of course) filled with impromptu karaoke sessions over the PA... oops did I just say that out loud?
Yes I think a simple addition of basic diagrams for this eventuality to the IFE would do the trick nicely... especially if said Auto announcement is only in English (can't recall it now but I think it can be done in other languages but I'm not sure if this is dependent on the route) and whether it's something which has to be manually done through the IFE control system... on newer aircraft I'm sure it's automatic but you just never know!
Something to the effect of the pictures on the safety card, flashing on the screen with maybe the words 'DO THIS NOW' in a few major languages might help...