Yes. Typically, a will is drafted so that it applies not only to any current children but also to afterborn children. In a statement of family, in a Will, I would often say that:
"children" as used in this Will including the following persons and any other person subsequently born to me or legally adopted by me.
Then I would draft the guardianship and dispositive provisions using the term "children" without specifying a name.
If children are born, but there might be a paternity issue, it isn't uncommon to state that "my children at the time this Will is executed are . . . . and I intentionally exclude from benefit hereunder or for any fiduciary position with respect to me, any other person claiming to be a child or other descendant of mine as of the time that this Will is executed, but do not intend to exclude subsequent children or children later adopted by me."