This is not a problem. We are not doing a run through the wilderness with a bunch of twisties. Well, there is the on ramp and then there is that part between Georgia Ave. and 270 (below the Mormon Temple)....
Sometimes people will have an extra that they are willing to loan out (since the the 2-ways usually come in sets), just make sure you return it to the owner when you get to the end of the run (lunch).
Not having a 2-way only means that you are not hearing the conversations and comments... about why we had to stop or pull over to the side of the road, who we are waiting for, that &%@ SUV messing up the photo-op by breaking in our line, the minivan "with an obnoxious amount of stick people on the back window", the %)@$# farm combine going 3 mph ahead of us, Marco.... Polo, etc. They do add to the fun and experience but are not required.