Thanks so much, Claire. We do have those 3 birth/baptism records, and have copied many more as-yet-unconnected Armstrongs from Quebec church records in the Drouin Collection. You never know when you may find another family that's related. Every bit of information is helpful!
We haven't yet found a mid-1850s birth/baptism record on David J. Armstrong & Mary Ann Waggoner's son Wallace. Wallace was age 16, born Canada, in the 1870 Franklin Co., New York census. In the 1900 census of Ramsey Co., Minnesota, he said he was born Oct. 1854 in Canada.
There were probably other children born between the last known child, Wallace, in 1854 (when mother Mary Ann was about 30), and David J. Armstrong's death in 1866. At least there were probably other pregnancies. These children must have died young or at birth (if carried to term) since they weren't with mother Mary Ann in the 1870 Franklin Co., NY census. We don't have any records of these possible other children, and may never know.
If you see anything else about Armstrongs in this area, I'll be glad to hear about it!