You use DLNA to watch videos/music/pictures on your TV which are stored on your computer. Sony excels at it, Panny does not. It's probably already built in to your smart TV. Not sure what DLNA options there are for phones. There are probably quite a few. I guess Airplay is a bit like DLNA but not the same thing. But I'm old, so I don't see the point of watching a movie on a 3" screen when you could watch it on your 60" screen.
For your current system, I'd skip RCA and run HDMI from the player to the TV, then optical from the TV to the stereo. You can simultaneously run RCA to your wireless headphone base and you should get sound on all outputs. If you're lucky, your TV may even bitstream DD/DTS 5.1 from it's HDMI inputs thru optical to your stereo. Mine does, and many other recent TV's do as well. My stereo is a lot older than yours and still works beautifully with the optical out from my TV for all sources. Worst case, you can run optical from the player to your stereo and bitstream surround while still getting audio over HDMI and RCA. Not a problem.
Personally, DLNA saves me a couple of bucks a month off my cable bill since I can watch my recordings from my PC without using a cable box. I can also watch any shows that I download and access all my music and photo libraries. It's pretty handy. You can do exactly the same thing today with your son's PS3 and PS3 Media Server running on your PC. I guess if you never used it, you won't miss it if you go with a Panny.
Like teachsac, I'm not a big fan of the sony menu system, but at least it's fast and will be familiar to you.