Easiest, would probably be interstate out of Lincoln to Ogallala or even Sidney, then straight up thru Alliance and Chadron. I don't like interstates with my Harley so I normally pick from these routes: highway 2 all the way to Alliance then north thru SD. #2. Go north and catch highway 20 thru nebraskas sandhills for a beautiful/peaceful ride. Be careful to calculate the distance between towns and gas in your tank, especially on Sundays and late night rides, no allnight stations there. #3 Ride to Valentine then go north thru these South D towns: Mission,White River, Cedar Butte, Wamblee, Interior. Then ride highway 240 thru the Badlands and up to I-90 at Wall. Get your glass of water at Wall Drug and ride west the last 50 miles to Rapid on interstate. Route 3 is my favorite, much more back woods highways, scenery. But I am not sure if my wife would ride those quiet roads alone the whole way. There will be hundreds of bikers all the way, and I personally know you can handle us bikers just fine
Im guessing if my wife knew how to handle bikers, I wouldn't have ever met you!
If you want easy and no interstate, then highway 2 thru Nebr. to Alliance is faster, I think speed limit through much of it is 85-90 for Harleys. GRINS