The rooms are a good size so I would move in and position those pieces and then see what you need. The first step is to decide where you wan the TV if you have one. Of course because of the stirs that LR space will become much smaller. Could you post some pics of the space too.. You will need more lighting so table lamps and floor lamps for that , a light fixture for the DR. I need to know what the floors are , a pic of the kitchen . Since this is an open space all those things need to work together.