Actually, there is a designer who has designed a sofa/table piece. You can see it here - http://kononenkoid.com/julia-kononenko-projects/convertible-sofa. That may help you visualize your planned project.

First thing you need is a pad of graph paper to understand that there is no way the furniture items are to scale (exception could be the dining table) I'm guessing the kitchen is off to the left and the main entry is into the Drawing room? Can the wall be eliminated between the two spaces for more flexibility? - if so, the drawing room space would lend itself perfectly to a round dining table. But the main thing is to draw on graph paper the space & actual dimensions of the furniture you'll be bringing to your new home - so you are not shocked when you move in.

There is no average height for the table and chairs.There're height standards for all the furniture. The standard height for the table is 30" and for the chair, it is 18". The depth of the table should be atleast 36". It might be a little broad say 42" but not more. The length if the table is defined with the seats required. The chair seat size should be 16" with the back height be 30" atleast. It might be more depending upon the design of the table.

The ideal space for a 6-seater rectangle dining is 11ft x 14ft. This gives ample space all around the table and even can fit 8 people. So yes, a 14'*10' seems good enough However, this all depends on the size of the dining unit you are planing on.