What are you trying to achieve? If you want a good sound in the seating area, where do you normally sit? If you want a balanced sound through the whole space a different setup would be appropriate. 

I think I’m ideally looking for balanced sound throughout the whole space as I’ll be using the speakers when cooking, when sitting at the kitchen island, and when sitting in the living room.

Just two Era-100s aren't going to fill that large space well and getting a stereo image at your seating positions without further compromising the room-filling is going to be tough.

With that plan you might wall mount one over the sink window and the second across from it by the balcony door. Likely best used in mono mode but you could try stereo and let your ears decide.

If you are open to four, then similar mounting spots, centered on the other to walls will do a lot more to provide even sound across all seating positions. Again, mono might be best but you could try stereo and different pairings to see what sounds best.

I assume this floor plan is not new construction. So, cutting holes in ceilings may not be an option. The diagrams below show to options for coverage. The rectangles are Sonos Fives in stereo pair. The circles are Sonos Era 100’s in stereo pair. Each pair of speakers are independent of the other but can be grouped to play altogether.

You may find the Sonos Fives to be more than enough for the entire space. However, the Era 100’s can be used for subdued listening at the kitchen island while eating (or blast them as loud as you want) 

I like that second plan with the Fives by the balcony it would give a pretty decent area at the couches and in the kitchen that see a decent stereo image.

As cost may be a factor this third option uses four (4) wall mounted Era 100’s in the main area. If wall mounting is not an option stands can be used. The red arrows within the circles indicate the direction of fire. Also note the suggested stereo pairs.

If two Era 100’s is all the budget will allow I’d place them to the right of the seating area (birds eye view) in the corners on either side of the window as a stereo pair. Preferably wall mounted.

The green circles in the kitchen are optional Era 100’s in stereo pair.

As mention before all stereo pairs are independent of the others. However they can be grouped to play altogether.
 

For that scenario, and with just the two speakers, put them in diagonally opposite corners, one in the kitchen and one in the living room in the corner near the balcony. 
Era100’s play stereo from the one speaker, so don’t stereo pair them. Use the as a group (of two “rooms”). Play about with how you angle them to see how the sound bounces off the walls.