We returned back to the uk just short of 3 and a half months, like you are main issue was our children's happiness. We too were told in time once they were in school and made friend's that they would soon settle, Sadly not for us. If anything they got worse, ours were 11, 8 and 6 years old, and it was the youngest two who suffered the most strangely enough. Heart wrenching sobs every night, refusing to go to school, even though they did make friend's. My hubby and myself spent many a day weighing it all up, and in the end it was a no brainer.. return home and get our happy fun loving kids back again, instead of having these sulky bad tempered aliens we had been left with... Life is too short and we felt our kids needed a happy childhood, and who are we really to say we knew what was best for them, or anyone else for that matter... we know we did the right thing in returning, no regrets at all they have settled back into school, met up with old friends and have made new, and back to being happy fun loving kids, just how they should be.. had we forced them to stay any longer they may have ended up hating Australia, this way they do have some fond memories, who knows if one day they would like to return even for a holiday.
Only you as a parent knows how it effects your child/ children, some adapt with change and some don't, if you decide to return well at least you gave it a go, and not worry about the what ifs... Good luck with what ever you decide x