"Wireless" Speakers for Living Room and Kitchen set up.

One of my kids likes and uses Spotify and does not want to change. He’s moving into his first house and his dad (that’s me if you have managed to read this far) offered him a stereo set up for his living room.

I was thinking along the lines of a nice all in one streaming unit and decent floor standing speakers.

My son pushed back told me maybe some Sonos stuff would be nice. I opined I could do better than that. That’s where I need help please.

As it turns out, he’d like speakers for the living room and for the kitchen. He’d “like to come home and play some music from his phone."

He doesn’t think there’s Ethernet in the living room or the Kitchen. Almost all the speakers I looked at (so far KEF LS50 Wireless II and Technics CX700 Wireless Speakers) have Ethernet plug ins.

It’s looking very unlikely that Ethernet can be plugged into speakers; meaning some sort of mesh. Not ideal but doable.

Is it possible to have some sort of more traditional living room system and have some kitchen remote speakers work together?  

So my ask is what in the heck to get please. I was thinking around 5K but could go higher.