It's been a few years since I did the Airfoil trial.... I think when the trial is over, Airfoil continues to work, but it times out after a minute or something. So, it will still work for pushing out an announcement, but if you are using it to connect speakers for music, it will cut out mid song.
For announcements only, there are scriptable ways to push announcements directly to Alexa devices. I have an echo in the kitchen, 4 dots around the house and an echo flex in each kids bedroom. They announce when the doorbell rings, who enters their code on the keypad to get in, their chores for the day, etc. It works good, but there is a slight (30 second-ish) delay as the script has to run and communicate with mamma amazon.... Credit autolog for putting this script together. If you follow along on the post, it's pretty much cut-paste with the scripts.
https://forums.indigodomo.com/viewtopic.php?f=138&t=20535&start=16My python abilities are pretty much limited to command-c / command-v.
If all of your home audio speakers are echo/alexa devices, you can use Plex to listen to your home iTunes music collection. When you ask Plex to play an audio track, "Plex, play dubstep playlist", it creates a mini Plex player in the amazon device and will play the playlist you created in Plex Manager (which can run on your Indigo Mac, another Mac or in my case, on my QNap external drive.) Then say, Echo, play on all devices" and you get whole house that way. If you ask Plex to play a video/movie title, it will look for whatever video device is set up as your default player (living room tv, appleTV4, etc) and will start playing the video on that device. What I haven't tinkered with yet..... If you use the Plex Manager plugin, you can see it when an Alexa device creates a plex player. I haven't tried to use Plex (from within indigo) to push to my Alexa devices. I've only pulled it from the Alexa side. So that may be another option for pushing music out to your Alexa devices.
Sorry again about my lack of help on the coding side of your question.