Any luck choosing a color yet? Any pics you can share to get an idea of what you are working with?

I don't know how hot it gets in Auckland in summer (I've only ever been to NZ in winter!) but if it gets hot, then go for a pale colour. Dark roofs should be kept for cold places!

I would like a warm mushroomy gray with darker brown/charcoal for the trim and window framing. Also, trim the bushes out front so we can see where the front door is...

First of all I would like to say it looks like your parents have brought a lovely looking home. The colouring of the outside of the house it typical for it's age. I would like to suggest that you stick with a light tone for the outside but is the Yellow / Cream isn't working then perhaps consider going for a White with a tiny tint of pale green .... this will blend in nicely with the garden, window joinery and roof but it will not be stark white. Internally I am a bit of a cream on cream kind of a person because I like to add colour through my furnishings, knick-knacks etc but I have to say I did move into a home with a mint green carpet which suits my personality but is not all together practical with pets coming and going and a lounge painted a medium to dark mint and I really love that colour. Originally the hall ways and other room where a butter / cream and just making it a off white really boosted the light and spaciousness of the home. The lounge is still the same minty green and I think I will repaint it a similar colour as it is very relaxing and "natural". So go for something that is restful inside and something clean and almost white outside. Hope that helps.