Trump has stated his interest in mass deportation of authorized immigrants, including the National Guard.
In 2013, there were about 5 million U.S. born children of at least one unauthorized person (go here). Assuming 2 children per unauthorized parent, this suggests that about 2.5 million of the 11 million unauthorized persons are adults with U.S. born children. The number of such children (say to 6 million) and the number of such parents (say to 3 million) have most likely increased since then.
There are about 70 million persons under the age of 18 now. Thus, about 6/70 or about 8% of U.S. citizen children will be deprived of at least one parent.