For equal target transfer rate and range, I don't think there would be a mode that any WiFi tech beats BLE in terms of using less power.
If power is your concern, have you considered nRF5 devices?
Nordic has a proprietary profile for sending serial data over BLE (NUART) but AFAIK, you could only connect to one device at a time (not many).
Power isn't a huge concern, although it's a battery powered device, so having a longer battery life is a plus without needing to include a larger capacity battery.
I'll look into the nRF5. I've been using some of Nordic's code to test and build my prototypes already, although I feel like adding a proprietary profile on top will just make it harder to interface. Once I make the connection currently, all I need to do is enable notify on the specific characteristic which isn't too complicated (just a lot of code to actually get the characteristic)
If power is your concern, have you considered nRF5 devices? Nordic has a proprietary profile for sending serial data over BLE (NUART) but AFAIK, you could only connect to one device at a time (not many).