This is what I would do.

As for parking, yes you can park yourself in the park across from the hotel's front entry - make sure you get a ticket on entry (push the 'button' - don't insert your CC).

This can then be validated at reception which reduces the cost to that $20. It can be reduced by a further ~60% if you purchase at a store from the attached shopping centre and obtain a discount voucher (ask at the register if they don't offer) for each purchase.

But, even at this $7 rate, it is still per entry. Public transport is fine, albeit a 5-10 minute walk from the hotel to access. (You'll need a MyKi each)