Sub can go anywhere you’ve room where it’s not too obtrusive (recommend Sub not Sub Mini with an Arc Ultra), and the surround rears need to be at ear height, behind the listener facing the TV, to their left and right, turned in slightly. So in your case on Sonos stands behind and to the left and right of the sofa facing the TV. Anywhere else for the rears just won’t work for surround sound, no matter the space of the rest of the area.

I’ll leave others to recommend al fresco, but Sonance speakers most likely.

Thanks for the prompt response. Will the 100s suffice in this space do you think?

Looking for the option thats the least bulky.. also mindful of young kids touching the speakers in a high flow area. (Any recommendations with stands/mounting?)

Yes, Era 100s will be plenty. You could go for Era300s if you want full Dolby Atmos with their upfiring speakers, but Atmos and 5.1 will be incredible enough with the Era 100s. Hard to tell from the photo but Era300s could be just too much for the space in terms of their sound heft and bulkiness (with kids!) on the stands. Depends on your budget too…!

Edit: Sonos stands from the Sonos website will be very good but others can recommend…

Plug your Sub 4 (the minimum I think will be needed in that big open space) into an extension cord to make it easily portable, try it in as many spots as possible and pick the best sounding one. If you need more a second Sub 4 is easy to add.

I wanted 300s as my surrounds, tried a pair and they were amazing. Spouse was not happy with the space needed so swapped them for 100s. Sound is still very good but I do miss the 300s there. I moved them to another room as an Atmos pair and love them.

This is what I'm concerned about. What's stand/mounting kit are you using for them?

Our space is odd and not Sonos surrounds friendly. The only spouse approved permanent location is on top of bookshelves. Too high, too close together, not centered on the listening area. 

Whatever you choose, you can add a larger base to the stand and greatly improve stability and kid impact resistance.

Speaking of kids and Sonos related mayhem, you might want a Sub cover to prevent insertion of assorted toys. Cloth full covers in many colors are an option as are molded grills. I'm cheap so I sewed up my own covers using speaker grill cloth, about $5 each.