I wish I had this book when rearing my kids. It's not geared to parenting per se, but it is geared towards hardship and suffering, of which there can be plenty in family life. There's not a day when I pick it up that I am not blessed and strengthened.
"The Way Home" by Mary Pride radically changed my views on wife and motherhood. Now maybe it is theologically not reformed enough I don't know; I was a newish Christian, raised feminist/atheist, so, I was not as discerning as perhaps I am now. But man I loved that book. I have often thought to re read with my thoroughly reformed eyes but I loaned it out so long ago and did not get it back. . .
This isn't about motherhood per se but the "Give me Jesus" journals by Well-Watered Women has been immensely helpful for my wife daily in keeping her nourished on Jesus as a mother of five. It's gives helpful structure for her for prayer/Scripture reading. She also greatly appreciates Jen Wilken bible studies.