Scopes were used in the war, but remember they were used for long range shooting. At muzzle loader hunting ranges of 100 yards or less I don't think a scope will be of any advantage. The traditional scopes especially have a narrow field of view which will be a disadvantage at close range.
I am glad however that you want to use something traditional, rather than slapping on a 4-12X Leopold!!
If you are having vision problems, consider using a ladder type peep tang sight, such as the ones on a Sharp's rifle. They look neat, or "at home" on a ML, and you can enlarge the peep quite a bit to make up for loss of vision. Even with a large apature a peep will still be quite accurate. The rifle will certainly handle better than with any kind of scope, especially the old type that runs almost the full length of the barrel.
Again, if your vision is normal, I don't see any advantage to using a scope for shots under or at 100 yards. Open sights are faster, work when they are wet or fogged up, and are much harder to break or knock out of alignment. Open sights don't get in the way like a scope either.
Good luck.