Which Bluetooth micro controller?

Hi folks,
I'm moving on from my uno stand-alone. I need to design two neoprene sleeves that alert the wearer to timing. Around the wrist, one with a red LED one with a green.
They will be controlled by a waist unit that simply controls the frequency of red / green flashing, i.e. it has a pair of faster / slower buttons.
I'm a Physio not an engineer, if it takes a year to learn that's OK. At this point I just need to buy the right three units.
So, a master and two Bluetooth slaves. Adafruit seem to do small stuff? Regards, Al.

Does it have to be Bluetooth? The reason I ask is because the Wemos D1 Mini is very small, and although it doesn't have Bluetooth you can link them together wirelessly using ESP-NOW.

While you can have a master bluetooth working with two slaves, you have to work it so that it is only talking with one at a time. You probably don't need bluetooth, you just think you do, and using an NRF24 network or something WiFi like that described above is probably more appropriate.

BBC Micro:bit ?
Or the Adafruit stuff is probably fine...
I'm not sure that all of the "BLE" stuff is capable of being both "master" and "slave" - worth checking whether they can talk to each other, rather than just talk to something bigger (like a phone.)