By the time you've earned the income, it is basically too late to decide who it belongs to[*]. If the assets belong to one person, income from those assets must be declared by that person. If you earn interest on a shared account, you must declare 50% of it each. And so on. (If you're tempted to fudge it bear in mind that banks report to the ATO about interest paid and account ownership.)
I don't think Family Tax Benefits are taxable income, but I don't get them myself so I don't know.
What you can do is think about how you want things arranged going forward. That means making a prediction about who will have the higher income; it sounds like that's going to be you, and she will be working at most part time.
Therefore she should hold anything that generates taxable income (bank accounts etc) and you should hold anything that generates losses (negatively-geared investments, charitable deductions, etc). You could look into making a voluntary super contribution into her account which (imbw) will be deductible for you and get it into a lower-tax area.
If you're earning on the order of $30k per annum in interest you're looking at paying $11500 tax on it if it's in your name vs $5k if it's in hers, so it's not a moot point.
$420k in cash is arguably quite a lot, and perhaps you want to look at putting some of it into a low-cost balanced managed fund, such as those from Vanguard. That will be somewhat more tax effective, though less stable. If you're looking to buy a new house within a few years perhaps cash is the best place for it.
[*] One kind-of exception is that if you have a family trust, the trust can decide at the end of the year to whom it will distribute its income. However, you still have to decide to establish a trust in advance.