What you may get a handle on very quickly here is that Bluetooth is not for distributed audio, it's for point to point audio. You can't connect across multiple devices on the fly and have different things working in different ways. That work is not part of the design of the units. They are meant to be very simple paired devices.
So, to add wireless home options you will need devices designed for this. The Chromecast Audio (discontinued) was one of the best and cheapest options to do so. You could stream wirelessly from your phone to one or more of the units at the same time and control volume independently in each location.
The same is what
@panteragstk recommended with units that are in production.
Like your current set of powered speakers, you will need to get speakers which can have a device plugged into it. Heos and Sonos are very popular devices for doing this. I haven't played with Echo in doing this, even though I have a number of them in my home. I probably should. It may be a nice inexpensive option for you.