For Sonos, my Understanding is you will need a soundbar to connect to the TV itself - probably the beam in your case - then you can connect any number of Sonos 1’s (or whatever they call their cheapest speaker nowadays) to that system, which would be perfect to add to a kitchen. However, this whole set up is $$$ since you need the soundbar for the TV. The individual small speakers cannot directly communicate with the TV - only the soundbar, which in turn is connected to the TV. That said, I have $$$$$ worth of Sonos in my own home and am happy with it. :)

Can't see your drawing, out of focus. But, I would put in several hard-wired Ethernet points and one central WiFi router. You can always add more using one or more of the Ethernet ports.

My bet is that that a large percentage of customers for these products are those with hearing loss and very many as a consequence tend to be older individuals. I'm not so sure describing a product as "for seniors" is any distinction. The product linked uses Bluetooth, which has limited bandwidth and so likely a lower sound quality than other similar products that use a different RF frequency/standard. As far as power supply is concerned, the TV needs one and so one must be available in the cabinet. For many of the products, the base station is also the charging station for the headphones. WIth a TV located in a cabinet, that probably would be a feature to avoid.

The Honeywell T10 Pro thermostat with remote sensor(s) will do what you want, I think. You will wire the thermostat to the humidifier and adjust all settings there. You can place the battery-powered temperature/humidity sensor(s) wherever you like (within range) and configure the thermostat to manage the temperature/humidity levels based on the sensor(s). You can program the thermostat to switch temperature/humidity control among between the thermostat and among sensors based on a schedule or motion sensing. Note that the thermostat requires 24 volt power so you will have to user a transformer (example) to power it.