Welcome to AudioHolics! And thanks for the photos & floor plans. They help.
I've heard the passive LS50 version of your speakers, and I like them. I'd keep them, add a subwoofer or two. One sub is probably needed, two can be nice, but aren't required. It depends on how well one sub works in your room.
For future expansion, I'd also plan on using the KEFs, either as front left & right speakers or as rear channel speakers in a larger surround sound system in your family room. To keep things simpler in an expanded system for the future, you might want to consider passive KEF LS50s instead of the wireless ones. Remember, those speakers receive signals from the source wirelessly, but they also require electric power from a wall socket.
If it were my home, I wouldn't want a full surround sound system in the bedroom. You might want music there, but a smaller & simpler system might be all you want. It does depend on what you want, and what else the GF wants in the bedroom. So, wait and see.
Don't read too much audio stuff online too soon. It's purpose is deliberately designed to make you want to buy more stuff – and it usually works

. And don't overthink things now. Wait and see how things develop in your new home.
Finding an AVR with WIFI and ability to connect to a laptop should be easy. Most of those should be able to run a 7 channel system plus 2 subs. Looking at the room sizes you have, I think 5 channels would be enough. Seven channels work better if you have two rows of seating, such as one sofa behind another. But most decent AVRs available now do handle 7 or 9 channels. AVRs such as the Denon
AVR-X3800H or
AVR-X4800H should do the job for you. Similar Marantz (owned by the same company as Denon) or Yamaha models are also good.
In the long run, if you end up with front left & right speakers that need more power than those AVRs can deliver, those models I mentioned make it easy to add external amplifiers to what you already have. That way, those AVRs can easily work as pre-amps.
I also suggest you avoid jumping into Atmos until last, if ever. It will require mounting overhead speakers in the ceiling, and depending on what AVR you get, it may require external amplifiers. Personally, I don't think Atmos is worth that extra expense. Others will have their own opinions.
It will be well worth it to spend most of your speaker money on the front Left, Center, and Right speakers, as well as sub-woofers. Rear channels and/or Atmos channels are where you can spend much less, and not loose out. Ignore salesmen or audio advice that urge you to overspend on channels other than those front three.
Very good idea.