The Roam is a very small speaker with commensurate sound. Two or three Moves would be far more suitable for your large backyard. Assuming your home Wi-Fi has a strong signal outside, you can sync the audio across multiple Moves.

I had originally thought of using the amazon tap, but they apparently don’t make them anymore.  I was always impressed by the volume of that device.  I had thought of using 4 of them together.  Then I thought of the Roam, since I have other Sonos devices in the house.  But, I like the idea of only needing 2 moves to start, and then I can grow the system as needed.  If I start to get out of range of wifi, I can add an outdoor access point.

The added benefit of the move is that it won’t brick in 18-24 months like the Roam. 

Okay, thank you both for all the info!  I think you have sold me on the Move.  The only follow up question that I had was to wonder if the charging station for Move is waterproof?  Or, at least water resistant.  I have seen some wall mounts, and was thinking if the charging station is waterproof, then I could leave it charging, powering it from wires I have that were exterior lights that broke.