I would not worry about that, all it takes is a bit of leather cleaner (Lexol is great), 15 minutes every 3 months and you keep your light seats like new.
My wife had a CX9 with light tan interior that we bought when my kids were born. We sold it after 6 years with the seats still looking like new. Leather is easy to clean. BTW black seats get dirty too, it just shows less but the grime is there

I never had a black interior since I really don't like the darkness and the lack of contrast (the G70 Sport is the first one that I am considering since the grey quilting and the black piping provides visual interest) but transporting young kids is not a factor for choosing the interior color since I know how easy it is to clean (and I am busy and don't find as much time as I would like to detail my cars)...