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

Love your style and you've got some beautiful furniture there! A deep aubergine purple velvet on your wingbacks would look stunning. I'd tend to stick to purples in this area to keep it classy. Also, a dark purple would be more practical with kids than a cream. I'd keep the chairs you've got, unless they are really wobbly. Get someone to check them out and give you a quote for repairs and then you'll have a price to work against to see if you can get cheaper. OnePlan is right on the style and yet I don't think they look out of place in the room. I also like the idea of bench seats or if you wanted something really different, you could get a church pew?! I don't think the room has too much dark furniture as it is a large light area. Keep us posted with pics/samples of possible fabrics you find. Also, check out fabric outlet places.

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 :)

Looks good! Never seen distressed wood before.