We have always spent our DLR days consecutively and we love it, BUT it always wipes us out. Next time, we tell ourselves, we will plan a sleep in, relax by pool day in the middle of our DLR days - but we have not yet done this.
DLR touring is so tiring because every day we get up early and stay up late. To maximize our time and take advantage of when the parks are less crowded, we get there before opening, usually take a mid-afternoon break at the hotel to recharge, then stay at the park til closing. In the summer, these hours mean not as much sleep at night and hot weather to wipe us out, so the afternoon breaks are a must. In September, the weather is still quite warm, the parks aren't as crowded (except weekends) and the hours aren't as long (see
https://disneyland.disney.go.com/plan/tips/when-to-visit/), so it might not be as tiring for you.
Which hotel are you booking? If it's one with a nice pool, I'd put a lazy morning, relax by the pool, early to bed day in your itinerary in the middle of your DLR days. The kids might want to go to DL for part of that day, but try to make it all day without going. My guess is that everyone will appreciate the next full DLR day so much more with a whole day away from the park in between. With that lovely Australian 10 day pass, you could spend part of your "relax by the pool day" in the parks if your kids were desperate to go, but make sure you don't stay late. One day of a lazy morning and early bedtime sounds heavenly.
Non-Disney options: Are your kids boys or girls? I've got two boys and they would hate a shopping day. I've never liked Knott's, and Six Flags is mostly high-thrill roller coasters. We've taken our kids to
Legoland, SeaWorld, the San Diego Zoo, and Universal Studios. Last August, we did all but the zoo in addition to 5 consecutive days at DLR. Exhausting! More importantly, everything non-Disney pales in comparison to DLR. The parks aren't as expertly planned, as efficiently run, as fun, as magical, or as full of things to do and experience. So expect your kids (and yourselves) to be wishing you were back in DLR if you do DLR first and then go to another place. We always save the best (DLR) for last.
I'm glad to see you aren't considering a SoCal beach day as one of your non-Disney days. It would add the stress of SoCal traffic which wipes out the relaxing factor a beach day promises. Plus, you've got a week in Hawaii after your time in SoCal and Hawaiian beaches are so much better.
Another suggestion: unless you're only visiting DLR, don't stay in Anaheim the whole time. It's a lot of time in bad traffic to get from Anaheim to San Diego or Universal and back in one day. I would stay in hotels close to the places you intend to visit, then stay in Anaheim only when you'll be visiting DLR. Except for DLR, Anaheim isn't that nice and you'll pay a lot more for a lot less in an Anaheim hotel just because of the location. Our Marriott in Carlabad (near Legoland) was luxurious and cheaper than the motel we stayed in at DLR. Plus, if you're in Anaheim, the kids will want to go to DL and not the other places on your itinerary.
Staying in Anaheim the whole time has one advantage: you get to unpack once and don't have to deal with switching hotels. Here's a tip to make switching hotels easier: pack one suitcase with all your swimwear and toiletries for the whole family. Pack another small suitcase for just what you'll need at the other hotels. Then, when you get to each hotel, whether it's one night or two, you don't have to open all your luggage. Just live out of those two suitcases. When you finally arrive in Anaheim, unpack your bigger suitcase(s) with your clothes for DLR. You could even keep your Hawaii stuff separate and not open that/those suitcase(s) until you arrive in Hawaii. Packing this way also means you've got enough clothes so you don't waste precious vacation time doing laundry.
Another reason to switch hotels: If your kids are like mine, they will want to head to DL the second you arrive in Anaheim. They are always so excited to finally be at DL, it's hard to tell them to wait one more day. So unless you arrive at your Anaheim hotel in the evening, you may find yourselves heading to DLR as soon as you check in. If this is your first day in SoCal, then it will be very hard to save DLR for last. And, after traveling all the way from Australia, you'll likely be exhausted on day 1. If you stay away from Anaheim the first few days, you can spend your arrival day recovering from the long flights, enjoying the pool or visiting someplace that isn't as vast or tiring as DL.
Happy planning!
We will now split the week up as follows and each day we plan to be back at the hotel for 3 to 4 hours of rest in the afternoon.
