I think that any bikes you come up with will do the job. The wider the gear range the better. Mountain bikes with lighter tires should work just fine. Road bikes pulling trailers should work fine. Who keeps up with who probably will depend more of the fitness of each individual.
My first extended bike trip (over 2 weeks) was in 1968 when a high school buddy and I rode from Arlington VA to Land 'o Lakes WI. We had no bicycle travel experience aside from membership in our high school youth hostelling club which involved short overnight bike trips on the C&O canal and an occcasional week trip of hostelling in the PA Dutch country.
We just did it. There was no Adventure Cycling Association or Bikecentennial to go to for information. There was no internet with multiple discussion boards to ask others how to do it. We used whatever 10 speed bicycles we had. (10 speed then meant 2 chainrings up front and 5 cogs in the rear). I think I was riding a rather high end Schwinn Paramount with sew up racing tires, a Campagnolo racing crankset and a 14-24 freewheel. My buddy probably had a low end 10 speed Gitane or Frejus. That's all you could find those days in the DC area. We had a blast!