I'm back in the UK now but was overseas (Asia) until the DCs were 8 and 4. I used to come back to the UK for an extended trip every summer for 4-6 weeks, and DH could usually only come for 2 weeks of that, so for at least one of the flights and half or two-thirds of the holiday it was just me and the DCs. I based myself at my parents' house, but also went to visit old friends in London etc.
Yes, it's tiring, but it was worth it. I suppose the entertainment thing depends on what is available where you are staying - my parents live on the outskirts of a large city, so it was very easy to spend a few hours each day going out and doing something, like visiting museums, parks, zoos etc.
Meeting up with cousins or old friends with children also helped - the DCs tend to get more bored if they don't have other children to interact with. If you don't know anyone with appropriate aged children, are there any activity sessions laid on at nearby museums/country houses or whatever? There is usually something going on in the school holidays.
Or take a little side trip, just one night in a B&B somewhere - preferably somewhere very unlike anywhere you would go in Australia, eg somewhere with medieval castles or steam trains or whatever.
Or if it was a wet day and I didn't feel like taking them out anywhere much, a trip to a charity shop or pound shop for books, jigsaws, craft material etc was usually enough to keep them entertained for the rest of the day. My parents would then re-donate stuff to the charity shop after we left. They also made full use of the fact that my parents have cable TV with lots of channels they had never seen at home. The 'entertaining' thing does get much easier as they get older, I found.
I can't offer any advice on homesickness and how the trips back to the UK make you feel about going back to Australia - I was very happy living overseas, and only moved back here because DH died and it was not possible to stay where I was.