My understanding is that this smartapp can turn on a switch when a particular user code is used. Is that correct?
- Turning on/off switches when a user successfully unlocks a door (configurable per door)
If that’s so, you can do your notifications much more simply now that Amazon has created the equivalent of text to speech for their routines. 
You will create a virtual contact sensor which also has capability switch. That way when you use any smartapp to turn on the switch, the sensor will automatically show as open. Turn off the switch, and the sensor will show as closed. This will look like two different devices to Both SmartThings and Alexa, but they will automatically be linked.
You will then use the Amazon Alexa app to create an Amazon routine (not a smartthings routine) which will be triggered when the virtual contact sensor is open. And you can have your echo devices speak whatever you want to have them speak, either just one of them or multiples.
So you won’t need webcore or LANnouncer or Echo Speaks. Just the virtual device, a simple Amazon routine, and the app from this thread to turn the switch on when a specific user code is entered.
See the FAQ: