You may be able to use something like this:
http
/www.amazon.com/G-Cord-Wireless-Bluetooth-Streaming-Transmitter/dp/B010UP3GXC
Not sure if Bluetooth is workable for you. And you would need four of the devices: one to transmit (TX) and three to receive (RX). Meaning a receiver for each destination speaker.
So you would need only a single output port on the Raspberry Pi sans any stated requirement for individual speaker control via the Raspberry Pi.
The DAC would be serviced by a single Raspberry Pi port. The output would go to the TX via 3.5 mm connection cable. TX broadcasts to the speakers RX. Something along those lines depending upon the overall setup and the desired controls.
I think there are enough products (adapters, wireless transmitters/receivers, cables,etc.) to make your proposed speaker plan work.
Basically you just need to look at and map out the transistions that need to take place from source to speaker. Then match product specifications for each step along the way.
You may also run into USB power issues; very likely chance that the USB devices will require separate power sources.
Overall a bit cumbersome....