I really wouldnt do the ducting thing , especially if you arent converting to gas , build up of soot etc is an extreme fire risk and you might need fans to recirculate the heat - potential noise makers
If you converting to gas , it will cost as much as a no vent anyway , or perhaps a bit cheaper. A 900 mm wide normal gas fire will lose more than 1/2 its heat trhru the flue and will consume round a kg of gas per hour , currently a 48 kg bottle costs round R800 - almost R20 an hour!!!
The wow factor of having a fire in the middle of the room is high. You could also relocate the fireplace to a free standing one in the corner if you want wood or anthracite.
As to the dining room , you could use doors on rails that slide to either side and then have the whole entrance open (same with folding french doors)
The bedroom entrance would probably be well served with a trellidoor and 2 frenchj type doors folding against a wall - giving you a secure "inscape" area.
Maybe you should just tell the family that the family lounge is now your hifi room and to use the other lounge? Then you might not have the issues with aesthetics and ergonomics
