For a salary of 30K I would not suggest Discovery bay. Travel expenses are pretty high & mind you ferries will change for your 1 year old kids as well so just a return trip with fly to central would cost you around 150 HKD. Many IT guys on short term contract put up in Tsing Yi. A decent 2 BR flat (about 800 sq ft) would cost you around 8-8.5K. Make sure you select one with good club house facilities especially as you state your patner will at home with your kid. Grand Horizon in Tsing Yi a good place which I would suggest.
If you are looking for something different the you could try Park Island. Its a green island. They have 24 hours bus/ferry services to Central/Tsuen wan/Tsing YI MTR/Kwai Fong MTR.
The 2 club houses are definitely one of the best in HK. A 2BR flat would cost you around 8/9K while a 3BR would cost you 10-13K. These sites could be useful.
http://www.parkisland.com.hk http://www.pitcl.com.hk/eng/html/index.asp