Recommendations needed for home cinema interface

I'll try and keep this short!

My folks are building a new house, and it will include a large garage (separate building) with a bar room upstairs and a cinema room.

I have some experience with home media, so have already mapped out the cabling for the room and the sound and visual components needed. I intend for the ceiling-mounted 4K projector to have access to a number of sources for variety's sake - Sky Box (for TV, boxing events, etc), a NAS loaded with movies, Fire TV box for apps and streaming, and a few cables spare for plugging in Xboxes or PS5s/etc when the younger members of the family visit.

My question is this - my old man is not IT savvy at all and I can already predict the inevitable phone calls when he's confused trying to switch from one source to another using any one of the multiple remote controls which may be lying around. Is there any unified solution available which would present all the sources neatly to him onscreen via one remote/controller and allow him to access them all that way? Simplicity of access is key here, even if the tech behind it isn't simple.