I have a custom fact for notes. I call it Note.
I enter what I know, for example:
"No children" per 1928 Smith genealogy
No children in 1850-1870 census
Found "married" with no spouse 1880 census
Sally showed 0 ch born, 0 ch living in 1900 census
I try to stay clear of saying "no children" as an outright statement because one never knows for sure. This is especially true for
1) children born 1881-1885 who left home by 1900; but also for (missing the 1890 census will haunt us forever)
2) children born to family, wife dies, grandparents raise the child - never found in the census of either parent
3) Child given up by woman for adoption.
4) As for unrecorded children of men... well, that's always an open question - from one night stands to affairs (whether adulterous or not) to whatever.
So, I try to be specific with what I know.