I'd listen and respond specifically. With 1500mi underway they would/should be asking the questions to suit their needs.
In other words, if they asked for road map, I'd show them a road map. If they asked for a bike route map, I'd help them get one. If they asked for the fastest way, I tell them, if they asked for the most scenic, I'd show them that one. If they asked for the lowest traffic volume, I'd show them that route, if the asked for the route with the widest shoulders, I'd point that one out. etc.
If they were not that specific and asked for the best route, I'd ask what they mean by best, which would lead to the above type dialog.
Al