You've prob factored this in, but just thought I'd ask - is it definitely an extra 15 mins? What I mean is, the Donvale house might be further from the childcare centre/school than the Croydon North one so that could make a bit of a difference. A friend of mine (who also works in Richmond) moved from Thornbury to Kilsyth and she reckons because her childcare/school drop offs are much quicker, her actual commuting time is about the same.

I agree with a PP that an extra 15 mins on the train is no biggie (provided you get a seat) but it does seem a hassle when you're in the car especially with whingy kids and if you're stuck in traffic. Would you consider driving to the station and getting the train?

Personally, I would choose somewhere as close to the train station as you can, then you have the option.