Non toxic?
Sure...no insecticide is going to proven toxic to mammals if used properly
My prefered mite spray is safe to use the day of harvest, which means...we eat a lot it!
Your cats have no doubt been exposed to it on some lvl...
In reality, many plants are toxic to cats, i doubt some garlic oil would hurt them...
I think your fears maybe misplaced...
You can always spray with dawn and water, dish soap can make animals sick tho, I doubt it can hurt them either tho.
If you add cayenne powder to that mix, it'll taste bad enough that your cats will think twice!
They do look more like aphids than any other pest that comes to mind to me...how sad would it be if it took us this long to sort out that it's aphids! Ha