Before we moved to GC from NSW I did some research on GC one article summed up GC so well, you can find more culture in a yogurt than in the GC. Having said that the GC is a great place to live work and play.
South GC is much older and had a real Aussie laid back beach surfy vibe, North GC is much newer and still growing fast, loads of family friendly housing estates going up all over at really affordable prices, although there are a lot of established older suburbs that cost a little more. Schools there are good and bad as there are everywhere, are you going for public schools, church schools or private. As your kids are young and don't have to be in school yet I recommend doing some long term holiday lets in a couple of areas so you can get a feel for a suburb and DONT buy rent for at least a year. My kids are teenagers and we all love the GC there is so much for every one to do here.