I thought before Shikamaru mentioned both her parents seeking revenge in a ninja way if Sakura was killed, that only her father was a ninja and her mother was a civilian and thus her mother had a major influence on Sakura- her father being away on missions most the time. Being just a Chunnin, but with a family, he would have to take on missions almost constantly to support them. Sakura's mother perhaps worked at a low paying civilian job or as the anime suggested, had a small time candy making business in the home. From Shikamaru's statement I'm going to have to say her mom must have been at least a Genin (but tying into your thoughts a bit- she didn't come from a ninja family. So with a ninja father having very little influence on her and a mother who had a non ninja background having a profound influence on her, she entered the Academy with no ninja training whatsoever.) From what Kishimoto has said about Sakura's background, he basically just transferred the typical familial life his generation would have grown up in- into Naruto's world. Thus instead of her father being a salaryman he was Chunin ninja away most the time on missions, she would have seen him occasionally but her mother would have been the one there most the time.
I didn't really take Shikamaru's statement to mean that Sakura's parents had to be ninja in order to get revenge for her death. He was focusing on the cycle of hatred, and regardless of what her parents were, they would want revenge for the loss of their daughter. Not only that but he was also talking about Ino who definitely had ninja parents who would want revenge. Rather than stating the phrase in two different ways, it seemed to me he just made a general statement about their parents wanting revenge i.e. cycle of hatred rather then us getting an actual insight into Sakura's home life. I feel like it doesn't seem to be a priority of Kishimoto, especially since he hasn't shown Sakura thinking anything of her parents for a long time.
I sort of think seeing Sakura's family history is about as likely as getting a last name for Tenten XD