I use the TripTik website offered by AAA.
https://triptik.aaa.com/
It allows you to say you want to avoid highways. It will program in rest stops at a time interval, if you want. Sometimes, to force it to take a scenic route that I prefer, I add artificial destinations along the route that force it to go a certain way.
I think I had a problem in the past where it classified a 4-lane divided US highway as a "highway" and would not put my route on it. I had to remove the "avoid highway" option and then force it off of the Interstate roads. They may have this fixed now.
You can save the route and print out turn-by-turn instructions to give to others in your tour group, so that everyone has the same instructions to follow (you don't have to travel in a pack and worry about getting separated -- assuming everyone in your group can follow instructions and read a map!
).
As a AAA member, this website is free to use and store routes. I don't know how they handle non-members.
You can also use Google Maps. Tell it you want to avoid highways. Once it creates a route, you can grab the blue line with your mouse and drag it over to force it to take a road that you prefer over one it chose.
The AAA TripTik web page is powered by Google Maps, but has a special AAA look and feel. And it saves and prints the routes better (IMHO) than Google Maps.