Is 4.5hr enough time to make a Domestic OOL to SYD to International T1?
 

I'm a US Citizen traveling to Australia with my family in a few months. We'll be flying into Sydney, then going to the Gold Coast, then onward to Hawaii and finally back to Texas.

I just want to ask those with experience, if this is enough buffer:
Qantas flight from OOL to SYD, with a stated arrival time of SYD 11:55am. We will have bags checked into that flight.

As far as I understand it, we'll need to collect our bags and go to International Terminal 1 (T1) to catch our Jetstar flight to Hawaii. It says we must check in at the counter, and since we have luggage we'd need to do that anyway (we've had the pleasure of shorter lines for when you've already checked in and are just dropping off bags, like at Haneda Tokyo with Japan Airlines, but no such luck with Jetstar it seems).

The Jetstar flight departs at 4:25pm. Is 4.5hr sufficient time to deplane, collect our bags, transfer terminals, check in our luggage at the Jetstar counter, make it through security and make our flight?

Thank you in advance!

Yes, absolutely.

Of course there is always a risk of delays as I see for example, today many of the OOL-SYD flights arrived 1-2 hours late. You could probably still make it with that sort of delay

As post above, 4:30hr should be OK, even with some delay.
If OOL-SYD-HNL on JQ is 1 ticket they may interline baggage, but do not expect much. Worth asking at OOL.
You will have to make your own way between terminals, by free bus or train (pay $)

Airport info SYDNEY (SYD) - amenities, transfers, transport Click to open the wiki

Thank you both, it is not on 1 ticket, they're separate 1-way tickets. One is with Qantas the other Jetstar, booked directly with the airlines not together.

I did fully pay for the fares with my U.S. Citi Prestige card, but I've read different results from missing a flight due a delay (connecting same ticket or separate booking, seems hit or miss in claim approval). And they recently changed coverage from 3hr delay to 6 hour delay. We're traveling with an older parent (70s) and 3 young kids.

Thanks again, it sounds like unless there's a drastic delay we should be fine.

A suggestion for this as I've seen people struggle with this stuff. If you can collect the bags alone (with a cart), send the remainder of the family to T1 and have them wait for you there. If you have mobile international text coverage they can partially check in and await your arrival with bags after taking the free bus.
The bus can get busy/full and it sounds like you have 5 or more persons (including young kids and elderly) so this part will reduce any stress of transport as you like'y will do most of the legwork anyway..