For chair scoot and sit space, I'd follow the guidelines for a rug - 4' all around. Then you want to be able to navigate around the table while people are seated, so add another 18" all around. Are you locating the table at the end of the galley? Maybe you could use a banquette on one side or in the corner https://www.houzz.com/photos/3rd-street-bungalow-traditional-kitchen-austin-phvw-vp~214425

The chairs are a good match. Leather is probably best, great for kids' spills and accidents, but any fabric will do. Not sure on purple with green - those two colours together clash a bit for me. The green kitchen looks great, and I'm a fan of dark wood. The only thing throwing it off at the moment is the yellowish coloured walls. If they were repainted a soft white, this would make the green and the dark wood really pop, giving you a fresh and sophisticated, calm look which I think would work well. You could then upholster in a green to match the kitchen which would look appealing. Finish it off by some fresh white flowers as accents in the room to draw the eye and you've got a beautifully transformed space with a fabulous feature dining area :)

Also take a look at Room and Board....they have several tables with different wood finishes or wood/steel/metal bases and a good selection of various tabletop materials. Also if you prefer a wood table, an area rug underneath the table could also help to break up all of the wood too.

we will replace chairs as well.....the space is quite a small area between kitchen and lounge....