On the morning of 9/11, I was at home in Minneapolis when my daughter's fiancé, Jim, called from Brooklyn.

"There's been a bombing at the World Trade Center," he said in a rush, "but Jessica is all right. She's in the city, but she's seven blocks away."

I had no idea what he was talking about. Within minutes of turning on the TV, I watched the north tower collapse, the clouds of debris threatening all of lower Manhattan. Where was Jessica? Seven blocks is nothing.

Fast-forward to August 2014. I am visiting Jess, Jim, and my grandchildren, Beatrice and Arthur, at their townhouse in Brooklyn — only a few blocks from the apartment Jim called me from.

"Have you been to the 9/11 memorial?" Jess asks. "They've just opened the museum, and I've been thinking about taking the kids to see it. They're probably old enough now. What do you think?"

What I think is that my grandkids (ages 8 and 10) are incredibly lucky — their young lives untouched by tragedy. A part of me wants to keep things that way. Another part realizes that their world will need to expand to include the realities of suffering, violence and loss.

"Yes," I say finally, "I think they'll be able to handle it. We don't have to see everything. And if there's anything that really upsets them, we can leave."

Our tickets timed, we walk quickly past the memorial pools to the museum entrance. I've prepared myself by reading a magazine article that describes the choice of exhibits, the endless discussions about what to include and how. For instance, there is a substantial archive of cellphone calls to loved ones from those about to die. The selected calls emphasize positive emotions. Further debate centered on whether to include information on those who jumped or fell from the burning towers. This exhibit has a room of its own, which visitors may bypass. We don't go in, not because we think that the children will be too frightened but because there is a waiting line, and we don't have enough time.

At first, the kids want to know the basics: what happened to the towers, how many planes were involved, why one of them crashed in a field and who was responsible. Jess responds to each question simply, adding at one point that she had been on the Q train heading into the city that morning and saw the towers burning. The kids' questions become more urgent.

"How many people died?" Beatrice wants to know, a question neither Jess nor I can answer precisely. "Did anyone survive?" Arthur asks. "Yes," we say, "many people on the lower floors (below the place where the airplanes hit) were able to walk out. There were a lot of very brave police officers and firefighters who helped them escape." "What about the people in the airplanes?" they ask. "No," we admit, "they all died."

And now I hear a new level of concern. "Were there any children in the buildings? Did any children die?" "Probably not," we reassure them. The buildings were filled with offices and the people who worked there. It wasn't a place for kids." Slowly, I realize that the artifacts of the museum (remnants of the building itself, a half-melted fire truck, metal twisted into fantastic shapes) interest the kids less than the human element.

Beatrice, 10, loves craft projects and is drawn to the multicolored quilts commemorating groups and individuals. Arthur, 8, is riveted by the photo wall, a panorama of portraits of those who died. Both want to explore the interactive site that allows viewers to scroll through the entire group and click on ones they want to know more about. They zero in on a pretty little girl, 4 years of age, who was traveling with her mother on the plane that crashed in Pennsylvania. They scroll away and then back — away and back — mesmerized.

Of course children died; I'd forgotten about the airplane passengers.

At the end of the exhibit, we find a table that invites us to write something on its surface. After a minute or so, these responses appear on a larger screen where everyone can view them. They appear like ghost messages for another minute or two — before disappearing.

Slowly, over the course of our visit, Jessica has been telling the kids about her own experience of 9/11. How she was headed into the city that morning to meet a friend; how she went to a building but no one was there; how she stood in the doorway then felt the ground shake, like an earthquake; how she knew what was happening as the South Tower began to fall. "Were you scared?" Beatrice asks. "Did you run?" "No," Jess says, "I felt calm. I thought I was going to die, and I didn't want to die running or screaming." The kids have already visited the exhibit that explains why the buildings fell straight down instead of breaking in two or toppling over. Their mom, seven blocks away when the towers fell, is standing right there beside them, unharmed.

Beatrice goes straight to the tablet and starts to write. "It makes me feel upset," she begins carefully and without hesitation, "that someone would want to cause so much destruction." The sentence has taken a different turn from the one I expected, posing a question to which there is no answer. She is pondering the mind of the other.

Instead of writing, Arthur draws a picture. Ordinarily, his drawings are full of mayhem — battle scenes with bullets flying every which way and planes dropping bombs. I expect the disaster of 9/11 to inspire a similar scene. Quickly he sketches the twin towers, not under siege, but beautifully and serenely intact. He makes them whole.

Back out in the sunshine, we pause at one of the memorial sites, gazing at the waterfalls slipping from view into the dark hole at the center. The kids don't comment on this. In the photo I take of them, they are standing on each side of their mother, smiling against the sun, holding close to her body, her arms wrapped protectively around them.

Madelon Sprengnether is a professor of English at the University of Minnesota. Her book "Great River Road: Memoir and Memory" will be published in the spring by New Rivers Press.