That will work for those purposes.  You may consider two One SLs behind the TV viewing area to get full surround sound.  A single One can only be grouped with the other units and will lag slightly behind for TV based audio.  I recommend One SLs for this purpose because the voice assistant is deactivated on surround speakers so the One SL, lacking the voice assistant, is perfect for surrounds.

I would go with what you have mentioned, but I would suggest adding two extra speakers to the mix, a Sonos One and a One SL 

Here is my suggestion…

Notes: One of the speakers in the Dining area is a ‘One’ and the three others are ‘One SL’s’ .. this would provide voice-control in all areas, plus the two ‘One SL’s’ in the TV/Lounge area should be ‘bonded’ to the Sonos Arc & Sub for TV surround sound (Dolby/DTS) .. I would put the two surrounds on ‘moveable’ stands (set at head-height, when seated) so they can be moved for the seating arrangements in that area.

I would also have the speakers in the dining area set at head-height when seated too, but these can be fixed or moveable… the two areas can play their audio independently of each other, or they can be grouped together for music playback.

That’s a pretty large space. I would consider using the two One SLs as surrounds for the Arc and getting larger speakers like a pair of Moves or Fives to use in the dining area. I don’t think two One SLs will be enough.

Hi

I like @Ken_Griffiths speaker layout but inclined to agree with @GuitarSuperstar about adding Five’s in the dining area; as well as the following suggestions….

TV Area

I’d suggest using Five’s as surrounds mounted at 30.5cm above head level when seated. Ideally surrounds would normally be placed at 76.2cm high and no more than a 30.5cm behind the seating area. In the latter Sonos Ones would be find (IMO).

However, given your room layout (and proposed positioning of the surrounds) I’d use Five’s here as well. Using Five’s as surrounds will not overpower the Arc. They will however enhance the surround affect. The Arc will struggle to accurately reproduce reflections in a room whose ceiling height is pitched to 3.5M and open on the sides (primarily toward dining area). The Arc works best in a room with a flat ceiling at a height of 2.4M to 2.74M and with much less openness on either side.

Finally, you might consider adding a second sub given the size of the space. I use two subs in a space much smaller than yours. Just make sure that one of the subs is new and not purchased from eBay (or similar site) as one sub must be a Gen 3. Also, using Five’s in this and the dining area (as suggested by @GuitarSuperstar) music will have a more seamless transition between the two during party events.

Dining Area

I’d suggest NOT setting the speakers in stereo pair. As the sound will come from different directions (front and rear) dinner guests may experience phase shift with speakers in stereo pair. However, dinner guests may find a fade of front to rear (stereo pair) interesting with certain songs. Also, the larger speaker vs the One’s will allow for lower volume levels (with fuller sound) for a more ambient effect during dinner. Voice control can still be incorporated by using an Alexa Dot or Google Home device with one of the Five’s.

I will now throw someone under the bus: @Ken_Griffiths can explain how to use Alexa to control speakers designated as different zones (Five’s not set as stereo pair) but controlled as an Alexa group.  Not sure if Google Home does the same.

TruePlay

In a space the size you are creating I strongly recommend using TruePlay via an iOS device.

Note: The TV area would be tuned independently of the speakers in the dining area. The dining area speakers can be tuned as a stereo pair or separately.

Hi

One more point since you say you are new to Sonos.

Sonos requires a strong WiFi network preferably without range extenders. However the latter may be a necessity in your new construction. The community can work with you to get the best network setup for Sonos using WiFi. 

If using your home WiFi becomes problematic there is another solution. It’s called the SonosNet. It can be established by wiring a Sonos Boost module or a Sonos Speaker to your main router. In your situation the Sonos Boost may be the logical path.

Only thing I would add is that for the dinning area, I would put the speakers (whether Ones or Fives) on the right side wall, rather than on two separate walls.  This will give you a sound stage for good stereo separation, rather than having mono audio coming from two locations.  If you don’t like that idea, that I might consider just getting an amp and ceiling speakers, depending on what the ceiling looks like.  If you’re going to use mono, I don’t think it will make much difference if the audio is coming from above or the sides, particularly for a dining table area.

Just some additional thoughts.  I think pretty much everything suggested will be fine.

@melvimbe 

Great thoughts. However, I don’t think they can use in-ceilings speakers as their post (to my interpretation) indicates that the area is open-pitched to the slant of the roof with no air space. In-ceiling speakers would have been my recommendation as well. 

Thanks everyone for the advice! Lots of food for thought.