Jen - the medical expenses tax rebate is one of the standard rebates available to everyone. As it's a rebate, not a deduction this means that as long as you owe tax, you can get 20% of ever dollar back over $2000 out of pocket (up from $1500 last year) - the pooled total medical expenses for anyone in your family, including children up to 21 (and more - see link below).

This means that you don't need to put it under your hightest income earner as it's not a deduction (which is where the higher the marginal tax rate, the better the return). As long as you owe more tax than you are owed for the rebate, you can put it under your own tax, but include your familys medical costs. Without wanting to be harsh, your accountant isn't doing a good job by not knowing about this, but most people luckily don't go anywhere near this limit.

Remember, it's not just for Medicare claimable expenses, it's also for things like glasses, prescriptions and physios if you are referred by a doctor.

Have a look here:
T9 - 20% tax offset on net medical expenses over the threshold amount