I just looked at the map (very quickly). If my memory serves me right (its been 30+ years since we lived up there), I think the North route should be fairly flat, farm country. But, believe me, I could be wrong!!!! Maybe someone up there could chime in.

The South route, on the other hand, is probably hillier (can you tell, I'm all about avoiding hills??). Didn't study maps on either route though.

I say, you may have chosen a great ride. You've got time to get some good training rides in this summer to get ready. I think you should be able to handle the mileage. Good luck!