For simple investment with strong returns the stockmarket is hard to beat over the long term. Perhaps a managed fund (group of stocks managed by professional investment managers) or an index fund (eg. ASX 200 can be invested in as a total). Comsec may waive or reduce the standard commissions and/or entry fees on managed funds. Pick a fund or system that reinvests your dividends to maximise the effect of compound growth over time. The ASX site has a great comparison of property vs shares over 20yrs. The bottom line is that both return high averages over the long term (over 10%).
As time goes on and you learn more you may like to add 'leverage' (borrowing some money to add to your own) to increase the size of the long term prize.
Great to see you thinking of your children's future so early.

Fringe suburb next to current boom suburb is a good start and bombs that you are confident you can fix don't stay bombs.
 
Scenario 2 (just because I see your potential) – 400k home with smaller deposit (say 10% paying the mortgage insurance), still a bomb but better location amongst 500k homes, do the reno, revalue at closer to 500k, use the added equity as the deposit for the next home to do it all again. Get a valuation when you move to ensure your capital gain to that point is Capital Gains Tax Free. The original home becomes an investment property with all interest and costs tax deductible and get great depreciation due to the renovation (lots of new bits). Learn about how a quantity surveyor can help you to maximise your tax benefit (especially with 'scapping' etc. with renos).
Scenario 3 etc. can now be designed by you, improving as your knowledge grows. All the best mate.

Do the maths very carefully Rafael. Your first priority is your family and being short of cash adds tremendous pressure and can lead to a financial loss (if you aren't able to pay your repayments the property will be sold by the mortgagee and you may get back much less than your contribution due to selling costs etc.).  Property investing is a great vehicle for wealth creation but not understanding the maths can be a serious mistake. 
Do up a budget on paper or Excel and see what you can afford to repay (on your income only because that's your plan, to have kids). At an interest rate of say 8.0% (which is likely based on Reserve Bank comments) and a loan of 330k you will need to pay over $500p.w. after you have paid all your bills (not easy on one salary, even a good one).  Renting somewhere cheaply (granny flat or with family perhaps) can turbo charge your savings (do the maths on what saving $100 on rent per week can do to grow your deposit). Also ensure your deposit is earning top interest while you are building it up. Get someone who knows accounting or budgets to check your figures. The maths will help guide you in regard to what you can comfortably afford to borrow and repay year after year. Even before we walk or ride we have to learn to balance. All the best.

Hi I,

1. Learn about investing until you fully understand the risks, costs and rewards before you begin. Reading a few books is a good start (you will pick up a lot more information than just asking the odd question).
2. Just when you think you know enough get expert advice. Seek out a mentor (who has successfully invested before) and/or an accountant to check your numbers (including tax considerations).