Hi, I know there are so many things to take into account and it's hard to get perspective from a photo. The white you can see is an extension with building paper, and the red is the existing building which is two story. The exterior is wide weatherboard planking, the windows are silver aluminium with very little trim. The doors in the front of the picture are French doors from bedrooms that will open to an enclosed courtyard ( yet to be built of course) The roof will be a light grey/brown but you won't see it much because of the flat roof style. There will be decking and ballustrades covering half of the new extension.

Now for Mr 16 months... I really can't decide. His room is going to be on the cold side of the house, with not so much sun so I want it to get that cozy sort of feeling when you come into it. I was thinking yellow or orange curtains? But then I don't know what colour to do the walls. These are some fabrics I like:

To answer your question I would paint the body of the house blue, all trim white, and then the "fringe" which I think ties into your porch decking, I would paint it the gray. It is a good "grounding" color for your home. Sherwin Williams has a cool web tool. Take a pic of your house and load it onto their site. You can "color" away on your house. When I painted my house for the first time, I did not want the garage door to stick out, wanted it to blend into the house. Everyone said it would look weird, needed to be painted the same as the trim. Used the Sherwin Williams site and realized want I visioned looked good. I have neighbors of dubious design skills! Ha! Ha!

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!