As far as using 1/2" ply for the boxes you'll be fine. Just use 1/2" for the back with dados into the side. All the cabinets I see built these days, except for us doing the customs, are built from 1/2". Whether I agree with it doesn't matter. Personally, if I was in your situation with all the 1/2" you have I'd make it work. Maybe some extra supports here and there but it should be just fine.
And yes the look has changed now for cabinets, the medium brown oak is no longer the look people want. Seems everyone is going either dark brown to almost black, a white or off-white, or depending on the style, like a shaker style, then maybe grayish/green or something similar.
Being a wood guy, I hate just painted cabinets but working with people more doing this stuff lately I've kind of looked at it a little different. And we built our house in '03, and we have medium brown oak cabinets and my wife hates the way they look and wants them Antique White, I'd prefer something darker, so we have compromised and decided when we get around to doing them, the cabinets will be the white she chose and the island I'll add will be a darker brown. So you can mix and match the colors also.
However, it is your daughters house, so you can try to steer her in a certain direction, but ultimately it's her choice.
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