Thanks for the replies, guys.
Quoll - I do have Aussie citizenship, so that's not an issue. My wife doesn't have any UK ancestry, so a spouse visa would be required. I'm sure I read somewhere that, if one parent is British, then you still get all applicable child benefits? I have to research the visa situation a bit more, though I know from media reports and the like that it's pretty onerous these days. I'm 90% confident that I could arrange UK employment from Australia that easily satisfies the financial requirements, so hopefully it wouldn't be too much of an issue for us.
Snifter, Skani - I get back once every couple of years on average. You know what it's like though - it's such a long way that it's only worth going if you're going for a few weeks and saving up that kind of leave is tricky unless you have zero days off through the year. It had also crossed my mind that my wife might not necessarily make friends with my friends or their partners. They've obviously met but it's been in short bursts of a few days here and there. It's also crossed my mind that I might not want to come back once we're over there "for a while" - not sure what I'd do in that situation. We do have a holiday pencilled in for September 2019 for a wedding, so could potentially do a recce at that point.
We have a pretty stable and secure position here - a house that we like and have a reasonable mortgage on, my job is secure and pays well (though it's stressful quite often), we have support from my wife's family with the boys.
Moving back would certainly make things uncertain - we'd have to rent, we'd have less support with the boys, different education systems and school age brackets, Brexit, air pollution etc. etc. On the flipside though, I would have more work-life balance in the UK - flexible working, 5 weeks leave as standard + bank holidays (the kinds of things that aren't available to me here), meaning I could spend more time with the family, which might help them to settle more easily.
I know I should do a pros and cons list and be objective but it's pretty hard, especially when feeling emotional about it. First world problems, hey?!