I'd say go for it @CocoLoco87. Australia is an easy country to move to - no language to learn, similar culture. Thee are adjustments for sure, but three years isn't as long as it sounds.
1-6 months - settling in, everything is new
7-12 months - feeling like you're starting to really live there
13-24 months - actually living there
25-30 months - aware you're in your last year and looking at doing things for the last time (last Christmas there, last school year etc).
31-35 - winding down
36- you're there but rushed off your feet attending farewells and organising all the last things related to the move.
3 years isn't that long.
However, as you may notice I have some experience if this, and I would HIGHLY recommend that you do not disregard what the poster above said about relationships falling apart. You are so much more vulnerable abroad than in the UK. We buy medical insurance before we spend two weeks on holiday, just in case the worst happens. Your relationship sounds great, but you need to make sure you're protected as a non-working spouse. If your DH cares about you, he will want this for you too.
I also know people - women, ALWAYS women - who have been stuck in countries because they have kids and are living abroad. You know your rights in the UK. You know that if you were to divorce for any reason at all (not necessarily cheating!) sweat the likely outcome would be regarding where you live and the school your kids go to. That all completely changes abroad. For example, your right to bring your kids to spend Christmas in the UK with your parents is determined by your then ex. He has to sign papers agreeing to you leaving the country, the dates you'll be away and the country you'll be in. If he says no, you have to accept it, or go to court. There are MANY other examples. Think that if you're not working and we're to get divorced, how would you get a work permit if you didn't have one? What would your eligibility be if you were no longer married? You know the answer to that in the UK, but I'm betting you've no idea about Australia.
They seem like nothing to do with you now, and that's great, but nobody ever gets married thinking they'll divorce, yet it happens 50% of the time.
I'd advise you to make the move, but also to first visit an international family lawyer to get advice on your position and what you can do to make it either similar to the UK, or whatever you want it to be. This is a massive boost to DH's career, which helps benefit from with or without you, so there's no reason for you as his partner to be disadvantaged in any way.
And remember, when you get there and he gets up that first day (and many others) to go to the office, meets people and naturally makes connections, you'll be settling the kids and forging out your own social life - it won't be ready made for you like his is. So, you already start at a disadvantage. Don't put yourself at any more of one than that.