Who writes the diary, and who falls behind?
Whoever was home logs the meal, whoever got up at night notes the fever, whoever went to the appointment remembers what the pediatrician said. Then in the evening you have to tell each other everything from scratch, and something always gets lost along the way.
"What time did he eat? Did you already give him the paracetamol? What did the pediatrician say?"
It is not about memory: the diary lives on one phone, and at home there are two.
One diary, kept up to date by both of you
You link the two phones once: from then on, whatever one of you writes shows up on the other phone too, with no messages to send and nothing to repeat.