I didn't check the actual 1880 census, but this is what I found on the CDs.
There was no Henry Cunningham in Coles Co in 1880, but this was listed was in Douglas, Bowdre Twp, IL in 1880:
Henry Cunningham, 59, PA-ENG-PA Elizabeth Cunningham, 64,wife, PA-PA-PA Mary Cunningham, 24, dau, IL-IL-IL Millie Hunt, 10, son, IL-IL-IL
You mentioned finding the Henry Cunningham family in 1870 in Douglas Co...perhaps the family remained there?I'm not sure about the 'son' Millie...I did notice you were also looking for some Hunts. Could this Millie be a grandchild (even though he/she is listed as a child?).
The only Cunningham born in PA that I found in Coles Co in 1880 was a Robert Cunningham, age 40, living in Mattoon.He was unmarried living in the Thomas McKee household.
Hope this helps and let me know if I can do anything else. Tracy