Hi Dev,
Welcome to PNG. My wife and I are from America and have been in PNG 3 months working for City Mission, PNG, a Christian NGO. So far we like it very much. The longer we've been here the more we get used to the city. There are many safe areas for the family to go shopping, or go on a picnic. You just have to be careful and learn where to go and where not to go. Don't leave items in your car and just be alert until you get comfortable with your routines.
Cost here are high. My wife and I can easily spend $250 Kina a week (USD $120) for food. We don't have kids so I can't help you there.
A typical Expat package includes salary, housing, car and fuel. Other than buying food and personal items the only thing you will need is things you want to purchase for decor. Cell phone and internet is kind of high here, but you may get those with your salary package. There are some nice restaurants and shopping stores here with international foods and electronics available. You can get almost anything you want...although more expensive than the USA.
Best wishes.