I have a similar "open concept" living area and it is not at all ideal for a "HT". It's fine for my purposes but I'd much prefer to have a dedicated rectangular room for HT.
Do the best you can and with decent kit you will have a good entertainment experience.
Make sure the WAF works otherwise you may have a system that is sub par and too many compromises that defeat your intent.
Good luck and keep us informed.
TV: Sony XBR 65X950G, AVR: Marantz SR5011, Speakers: front/Paradigm Prestige 15B bookshelf, center/Paradigm Prestige 45C, surround/Paradigm Atom, sub/SVS SB3000, DVD: LG UBK 90 UHD DVD Player, Media Player: Zidoo Z9S, Remote: Logitech Harmony Ultimate Home