One of the first things you will have to ask yourself is where you will be placing your dining table. A round table curiously seems to draw all elements that surround it towards it, thereby anchoring itself (and the chairs) visually more than a rectangular table would. It also takes up less space.
Wooden chairs, finished with a luxuriously quilted seat cushions, not only look pretty, they are fantastically comfortable as well, making them ideal for both formal and informal dining. The only aspect to be very careful about is the fabric covering the pads, as it will need to be washable. Nobody wants to deal with pesky pesto stains or tomato marks, long-term and family homes always seem to encounter spills.