It has been a difficult week for Ms. Vizguerra, 45, one of millions of undocumented immigrants contending with an uncertain future in the Trump administration. After she was convicted several years ago of using fake documents, Ms. Vizguerra, who has spent 20 years working in the United States, was ordered out of the country. But she was granted at least five postponements of deportation, and in December, her lawyer, Hans Meyer, asked for another.

Nothing happened. She was due for a regular check-in at the local office of Immigration and Customs Enforcement on Wednesday, and as the day crept closer, Ms. Vizguerra realized the possibility that she could be whisked onto a plane and separated from her three American-born children: Zury, 6, Roberto, 10, and Luna, 12.

Their care would fall to her husband, Salvador, 45, who works long hours as a driver for a tile company, and an older daughter, Tania Baez, 26, a preschool teacher with three children of her own. Unlike her younger siblings, Ms. Baez is not a citizen by birth, but she has a work permit under the Obama administration’s Deferred Action for Childhood Arrivals program, which President Trump criticized during the campaign but has not moved to end.

The last week or so has thrust the family into a state of extended emergency. On Feb. 5, Ms. Vizguerra called a family meeting over dinner, banning electronics from the table to convey the seriousness of the matter. The family cats, Miranda and Zayra, meowed as she explained the plan.

If officials were to come to the home in the days before the meeting at the I.C.E. office, no one should answer the door, she said. If they gained entry, Luna, a reedy middle schooler with braces, should use her phone to film the events. Roberto should open the emergency contact list in his phone and begin to call family friends and advocates. And Zury, the youngest, should go straight to her parents’ bedroom, close the door and stay there. “I told them, ‘I know it’s going to be difficult for you,’” Ms. Vizguerra said. “‘I want you to be brave.’”