We live in Trafford, son starts at one of the grammars this September. We assessed the situation in Year 3 and decided to stay / try for grammar, which thankfully worked out. Agree with other comments that it's becoming much harder to pass. We have one classmate who is bright / tutored / mock exams in advance, and just had a bad day and didn't pass. We have had 5 out of 30 pass this year (an unusual year but cohort specific), its usually between 1 - 3.
We're in a part of Trafford where the non grammar school options (for boys) are both Requires Improvement and would not be my choice at all.
I have a friend who moved to Cheadle Hulme for CHH, but I would cautious that Laurus Trust schools are very marmite. A different friend went to a Laurus secondary open evening and hated its very business like and lack of pastoral care feel. I also think Cheadle Hulme is a bit of a meh area personally. I agree Sale isn't the prettiest, but I don't think Cheadle Hulme is much better.
If I was you, I'd be looking at other well regarded local high schools e.g. Lymn High, Knutsford, maybe Wilmslow too. Otherwise, if you are thinking of jumping into Trafford, I'd be looking more at the Sale/Altrincham end, unless you only have girls, then look at Urmston/Flixton. You need to feel confident that you have a good back up non selective option, don't put all your eggs in one basket.
Also, look at living well within catchment. Your children are so young, you should plan for that furthest distance to strink over time.
Good luck!