How to make two small micros communicate with my Arduino over BLE?
You can use SoftwareSerial to communicate with two modules from an uno. But You will have to wire 'em up separately, not through your shield. (making the total number of bluetooth modules 4.

You could also use your existing sheild and poll between the two remotes. I.e. disconnecting from one and connecting to the other at a regular interval.

For the micros and bluetooth for your button, you could use a HM10 with an ATtiny like in this instructable. He uses two HM10 modules to talk to each other. HM-10 is a popular BLE module. If you want regular bluetooth(2.0), you can use HC-05.