OP said “Under documents, the largest culprit is iPhoto with 30some GB…”. These are your actual photos, of which only one copy exist (I.e. there is not one copy for iPhoto and a separate copy for Photos) - do not delete them. As @bowline said, it is safe to delete the iPhoto app. Also take careful note of @bowline’s guidance regarding iCloud Photos.
BTW 30 GB isn’t all that big: How big is your Photos library?