Is this West Elm sofa the kind of thing you are looking for? Or even lower to the ground? http://www.westelm.com/products/4227534/?catalogId=52&bnrid=3918508&cm_ven=Google_PLA&cm_cat=furniture&cm_pla=Sofas_+_Sectionals&cm_ite=West_Elm_Baxter_Sectional_Sofa_Cotton-Rayon_Ikat_Print_Feather&adtype=placi_src=17588969&ci_sku=4227534&ci_kw=%7Bkeyword%7D

I'm unsure if you're able to get them anymore! Did you end up finding them?

Love your style and you've got some beautiful furniture there! A deep aubergine purple velvet on your wingbacks would look stunning. I'd tend to stick to purples in this area to keep it classy. Also, a dark purple would be more practical with kids than a cream. I'd keep the chairs you've got, unless they are really wobbly. Get someone to check them out and give you a quote for repairs and then you'll have a price to work against to see if you can get cheaper. OnePlan is right on the style and yet I don't think they look out of place in the room. I also like the idea of bench seats or if you wanted something really different, you could get a church pew?! I don't think the room has too much dark furniture as it is a large light area. Keep us posted with pics/samples of possible fabrics you find. Also, check out fabric outlet places.

These spaces can look awkward but yours is quite inviting with those windows. It could become a retreat space, that allows someone to be near the action without being in it. Seating or lounging would work with the very low head height. I could imagine it would be a great spot for a couple of cool beanbag seats, a small funky bookshelf and a sleek retro lamp, or if you have children to cater for a games setup with storage in a retro ottoman.