If you have not already made this kitchen I would like to help, it lacks adequate storage for good pantry space. If you need a lot of fridge space I am not sure that is the best method as it takes up a lot of space. The idea of adding the bench for the kids is a good concept but the high back means the kids can't see you all the time and they will end up on your side of the bench so they can see you. Incorporating space for the kids at the end of the island bench would be more functional for both you in the kitchen and the kids would be able to see you move around and feel a part of things. Also how will they use this space kids don't just sit still they will want a bench or something they can use to draw do homework etc. Colour contract of light and dark always looks good. If you need help call I have a kitchen company called www.louisdivine.com.au. My kitchens are more traditional styles but I can do whatever is required and given the detail used in my kitchens my prices are competitive. P.S white bench tops are not hard to keep clean and they don't date, the nature of the stone itself is easy to clean.

I would personally stick to white cabinets... I know, not very original... but I think white works best with timber benchtops... and black/white/timber is a fail-proof/timesless combo imo... But if you wanted to inject a bit of colour... and based on your coastal theme description... then I would suggest maybe duck egg blue?... do a search of "duck egg blue kitchen" in photos on Houzz AU

Here are links to 2 older threads that may be useful to you. The common suggestion is steer away from cool or stark whites with this stone. It might be worth seeing how 1/4 strength antique white usa colour looks with Frosty Carina. Or 1/4 or 1/8 strength beige royal?? This colour at full strength is suggested in one of the links. It also is paired with antique white on dulux colour wall. [https://www.houzz.com.au/discussions/can-u-kindly-tell-me-abt-cabinet-colour-and-subway-tile-many-thanks-dsvw-vd~3344297?n=6[(https://www.houzz.com.au/discussions/can-u-kindly-tell-me-abt-cabinet-colour-and-subway-tile-many-thanks-dsvw-vd~3344297?n=6) [https://www.houzz.com.au/discussions/which-white-works-with-frosty-carrina-dsvw-vd~3982946?n=4[(https://www.houzz.com.au/discussions/which-white-works-with-frosty-carrina-dsvw-vd~3982946?n=4)

You could have one side of galley kitchen cabinets in a richer shade of white (I'll have to start looking at the choices) and the opposite side in a grey. Will you have overheads too? Then the subway tiles in a softer shade of grey than the grey lower cabinets. I'd love to see photo of door handles.