I agree, skip the ATV.
First most ATVs do not have the same controls. CVT, automatic and push-button electric shifting are all common on ATVs. Only the sport/race bikes seem to still use the traditional clutch and foot shift arrangment on motorcycles.
Second as mentioned riding one is nothing like riding a motorcycle. You have to really manhandle the controls and throw your body around to ride quickly. Or with the more utilitarian models at a sedate pace the controls are like driving a golf cart, with perhaps heavy steering.
If you want to break the learning steps apart, start with a scooter. It atleast is very similar handling characteristics to a motorcyle and the controls are for the most part just simplified from the full motorcycle controls.
Dirt bikes are a good way to learn at a slower pace without traffic and a softer landing. Small dirt bikes are much lighter than road bikes making the process easier.
Craig