You can always slap a filter on to get your wide establishing shot with the windows open, then black them out and use artificial light to light the actors using the windows as motivation. I a living room, you can also take advantage of practicals (household lamps, etc.) tor round out your lighting scheme.
I like to use soft boxes on actors for nice soft, even lighting that looks natural. These can easily be made using foamcore and putting some diffusion over the fronts. For diffusion, I'll buy a pillow-case cover for a couple bucks at Wal-Mart and cut it up. This will cover two soft boxes.