Actually, I have already thought about what would their kid be like, but it was just so briefly! However, it's entertaining for me to picture it. The information is for a male child:
Name: Probably something like Quan Chi's name. It derives from an ancient language with a meaning related to sorcery and/or metal-bending
Gender: Assigned male at birth. Probably cisgender.
General Appearance: This one's interesting. He inherits his height (6'9) and pale skin from his father, and his dark thick hair is inherited from his mother. (bushy eyebrows and hairy body). His eyes are crimson red by default, but he's able to change it. He has broad shoulders like his parents along with strong, muscular built.
Personality: Since I headcanon that Quan Chi is a genius, and Ombra's IQ score is way above average, there's a high chance that he's a genius. He's brutally honest, but meanwhile tries his best to be polite about it; though others may find it kinda rude sometimes. He has a bad temper but is also patient. He's pretty logical, and the fun fact is that he never really denies his emotions, he just rarely feels any strong one. He has a dry and dark sense of humor and is usually bad at making funny points. He's s street smart and a book smart at the same time. Also, he's an ambivert.
Special Talents: Well, he's 1/3 a demon, 1/3 Metalrealmer and 1/3 human, so this mere information can elaborate his powers and talents. He studies sorcery and necromancy under his father's watch, and is developing his iron-bending powers with the aid of his mom. He has a strategic and analectic mind which prefers to be an expert in mathematics rather than in human sciences ( art, literature, history, etc.) He can mix his iron-bending powers with his necromancy which makes him almost overpowered.
Who they like better: He loves both of his parents equally. He learns from both of them, and can experience dangerous but fun situations with them. He thinks his mom's sense of humor is better though.
Who they take after more: I think it's almost equal.
Personal Head canon: The cool fact is that he has Iranian genes! He has a curious nature, but at the same time it's like as if everything is already solved for him. It sounds kinda weird to him that how people enjoy 'little things"; there's bigger and better things to enjoy rather than the cool breeze in the morning! His only best friends are his parents.
Face Claim: I suddenly came up with Henry Cavill