I hope you’ve found your solution already since December. Still I would like to share how I’m using an AVB connection.
Since I wanted a parallel backup system, I needed both audio and MIDI interfaces that allowed two hosts at the same time.
So I went for a MOTU Ultralite AVB for audio using USB for Mac A and AVB for Mac B which works pretty well out of the box and with super flexible routing. Only when the connection is established (Mac powering up) or lost (shutting down) there are a couple of seconds of silence while synching. If the software crashed on Mac B, however, there is no synching pause, fortunately.
On the MIDI side I got an iConnectivity Mio4 and used its two individual USB-B connectors for the two hosts in the beginning. But now I only use its LAN connection since both Macs are hooked up to a network switch anyway. For Mac B I bought a USB-network adapter since the native LAN port is already in use for AVB.
No problems so far.
The level of success may vary. Keep in mind that, because two separate computers are not using the same clock, there will be some jitter. The plugins compensate for that, but at the cost of losing some frames, or stretching the stream a little. Furthermore the latency might be rather considerable, but for your kind of usage it is probably no problem