You do not have to have a marriage in order for the children to have a father. Marriages do not connect a father to the children.
I can't help you create the list you want 'cause I'm not very good at that either. However, wherever you can identify which person should be the father of which child or group of children, see:
p. 29, white paper manual for UFTree v. 3
"To enter parents for the individual, tab to the Father field and type the father's name,
or if the father is already in the project, you can find his name by typing the first few letter of his name,
or simply highlighting -unknown- and clicking the Find button on the Individual Record window. From the Candidate Individuals list, select the correct individual (for the father) ad click OK."
If the child has siblings, look next at the right side lower box in the child's record. That is a list of the individual's siblings. Double click a sibling and repeat from the above paragraph on adding a father. And again, until all of those children have both a mother and a father.