Hello Dee, I would 'mirror image' your plan and have the kitchen against the original part of the house (to the left of your step down) and still with the island. You could then have sliding doors facing both decks, and hopefully a beautiful outlook to your garden, also a lovely vista when you walk down the steps... your living dining furniture will have the feel of more room against windows, rather than boxed in by walls.

The absolute best position for a dining table is the 6 seater that Jen has positioned in her diagram. Nothing else will ever feel right. You could put a not too deep buffet in that recessed area where the bench seat is now , this will make the space all work as one large dining space.

Sorry but I am confused by the purpose and function of this entire space. Form follows function.... But I am not seeing the function being clear so that is causing the problem with the design. Your layout and comments imply that: someone is playing piano, someone is watching movie in theatre room, someone is playing with toys, someone is watching huge TV in living area, someone is cooking.... All at the same time. If so, then these needs will dictate the design... Or whatever your specific needs are. I would start by defining function priorities (storage, view, access, etc) and then work from there ~ prioritise these functions and estimate boundaries/size to define zones that are needed. Have another plan of things that cannot be changed easily - windows, kitchen, powerpoints - with dimensions from reference point. Ask questions like: how often will we/I use this _ do we really need separate piano room_ do we need to use French doors daily _ do I want to walk past new lounge suite carrying food _why would iI use both theatre room and living room at same time _ do I need all these windows or can I fill in one to get more function in the space _ Good luck as you will have to balance needs and wants!

The part of the home that you have shown, does not appear small. Room sizes are good. The problem is the kitchen in a thoroughfare, but it has plenty of storage. And the wall between sunroom and living. i would seriously look at removing the wall between sunroom and living, check with a structural engineeR. You said you do not want to remove walls, but this is the only way you can increase the size of that room. Maybe keep a supporting post in the middle, and work your furniture around it. Then install of full wall of storage on the dining/laundry wall.