iphone 4 disabled how to factory reset

Hi I've been on the site and none of the solutions I have found on the site seem to work to get into the phone in my case.

HOW TO ENTER CORRECT PASSCODE WHEN YOU SEE DISABLED SCREEN?

I have an old iPhone 4s 32MB (no cell service, but there is wifi, not sure it is connected though, not sure what version of OS it is, it's been inactive for about a year) and my son got locked out, we believe we know the correct passcode, but can't enter it from the disabled screen.

Local iTunes Connection = FAIL

I see there is a method to connect to iTunes and try but when I do, it states to authorize access from the iPhone to continue, but on the iPhone it is disabled so I can't authorize. The PC a year ago that the phone may have known at the time may have changed and that PC has been since replaced.

Find My IPhone Service = FAIL

I have gone to iCloud / find my iPhone and identified the device and set it for "erase my iPhone" but since the phone does not have cell service, this information is not getting to the iPhone to allow a factory reset.

Searched the many boards, but I don't see the answer. It is an older phone that had been sitting around, just found a need to use it, but can't get in. Don't need any of the data on it and I have the backup image in iCloud.