I have two Sony TVs (a 55" 2014 model w/ proprietary OS and a 65" 2015 one w/ Android TV).
I can operate both with the Siri Remote, and/or use the Sony remote to operate the ATV4 (navigation, playback controls etc).
The 2015 model with Android TV has one slight advantage over the 2014 one: It remains securely in standby mode. The older one has this pesky issue with ATV4 where it suddenly turns itself on during the night for no discernible reason, and remains on after the ATV4 has gone back to sleep (if it was even awake).
It's all pretty seamless and straightforward, and I'm rather happy with the setup. The only snag is that I can't get volume control to work over HDMI-CEC. Since every other aspect of Bravia Sync works perfectly w/ the ATV4, to the point of the remotes being interchangeable, I've no idea why volume control needs to rely on ye olde infrared. The only options on the ATV4 are "Off" and "Auto via IR". As a result, I can't control the TV volume from the ATV Remote app.
I don't know why that is, but I can think of tree potential answers:
1) Controlling TV volume from ATV4 via HDMI-CEC doesn't work with _anything_, be it Bravia, Vizio or whatever.
2) Controlling TV volume from ATV4 via HDMI-CEC works fine with every brand/system _except_ Sony/Bravia, because Apple hates Sony and all its customers and wishes that they'd all die in maximum agony. Failing that, they could at least be deprived of HDMI-CEC volume control.
3) Controlling TV volume from ATV4 via HDMI-CEC works splendidly with _everything_, including Sony Bravia, for everyone except me, because Tim Cook secretly hates me passionately so he made sure to upload special firmware to my ATV4 that disables volume control via HDMI.
If your muggle mom has no interest in controlling the ATV4 with the Remote app, this volume control thing is a non-issue.