Thank you to the two parties who responded to my inquiry. This is good info. It turns out my biggest suitcases are not as big as I thought. They are more like a 148. CM all around versus a 158 as is allowed with most international airlines. I have gone ahead and booked one Virgin Australia domestic flights so far (1 more to go). when you buy their choice fare, there is also an option to pay an additional 46AUD to give you choice extra with special seating preferred boarding and access to some preferred overhead lockers. With all that I think we will be fine and I will keep the weight limits in mind. Thanks again .