Before you even get started, your first day is very problematic.

Depending upon your exact starting and ending point, you're looking at a trip that's between 800 and 900 miles. That's far too much to be doing in one day, even at a sprint, and you certainly wouldn't have time to set up camp or do anything else that day. And the idea of doing ATVing that day wouldn't be possible, unless you can rent one around midnight!

You're looking at 15 hours on the road - factoring in only the bare minimum of stops. Even if you do it safely, you're going to be exhausted even into the next day making it very difficult to have fun on an ATV trail.

I'd strongly suggest you scale that first day back rather significantly - we recommend limiting yourself to 500-600 miles maximum for a full day on the road. The other days don't seem like they'd be that bad, and your return trip should be fine, but that first day is a real problem.