I'd recommend the 9W route, otherwise you'll need to ride on and cross part of the Palisades Parkway. Cyclist have been known to get tickets for it. That's all I have to add if you are planning a route. I've usually done it from Fort Lee/Suffern.
I put this into ridewithgps just for fun. From the MoTown area, it has me going through cycling classics like Irvington and Newark followed by Jersey City and Hoboken. Then basically up along the river. Over 90 miles one way.
I used to do this occasionally from Mahwah. The roads were all really nice from there. Some variant of Trailhead's suggestion could be good. Advise going through Harriman SP.
Haha, I though of doing the ride as an all nighter to escape the heat. I haven't ridden this much in about 5 years....road riding anytime is a pretty nice treat right now with the reduced traffic.