Hmma word of caution. I dont live inTun Mun but go down there frequently, and the whole area has lost a lot of the vibrancy it had a few years back. The Gold Coast has no rail link, and even in Tun Mun the West Rail takes forever to get anywhere. Youre dependent on the buses, or the perilous mini buses, to get down to TST or the island, and the road along the coast is a long and winding one.
Tun Mun is a fair step from the Gold Coast dont know if the estates run shuttle buses, services (they should do but check it) - otherwise its a tedious wait out on the road certainly a long way to go for a wet market!
Ive heard that the flats in Phase One are pretty run down, and $6,500 for 700 sq ft seems remarkably cheap, so take care.
It used to be quite lively but much of the night life has died away. Dont be taken in by glossy pics on the website. The beaches are drab and seriously eroding, and the Gold Coast shopping centre is tiny.
Your best bet is to take a service apartment for a couple of weeks when you come over and have a good look around. In particular let your wife get the feel of the place and make the choice as it sounds as if shell be spending a lot of time at home looking after the children.