Our 18 week old Sprocker bites my wife and son, but not me or our older son. We've tried stuff from the internet and training classes, with not luck. What can we do?

It sounds like your wife and son are regarded differently by the dog. You need to figure out what it is that's being done differently, and then correct this. For example, do your wife or son squeal when the dog mouths them (which makes them sound like squeaky toys and is very exciting to the Sprocker). Do you and the older son have deep voices and are firmer with the pup? Who walks the dog? Who feeds the dog? You need a root and branch review of the management of the dog so that everyone plays an equal part and is equally respected by the dog.