If she could have been a shield to protect him completely, she would have. Unfortunately for her, she was a smaller woman, and her son was already bigger than she was. The human shield idea didn't quite work as well anymore. But he was there at least, she could feel his back on hers, and knew that he was alright. She was almost positive he'd never encountered a dementor. They were one of those creatures on the list of things she never wanted him to have to deal with.
How many times had she seen them? On the train her second year, and then all through the school that same year. She thought they had been bad then. But facing them in the war, when the ministry no longer controlled them, it had been something else. Like this, only there had been more.
"I know." she said softly. "Remember, happy thoughts, clear your head of anything else." she said calmly, taking his hand in return and squeezing back gently. By now her wand was out, and pointed at the skies as the hooded figures came into view. She shivered slightly, ever since she had encountered them when she was only twelve, she'd hated them. But at least she knew she could beat them. There were many happy memories, and it wasn't hard to pull them to the front of her mind. The day she and Harry were married, the she first found out she was pregnant. When she first held James, and then Albus, and then Lily. There were many to call upon now.
"EXPECTO PATRONUM!"
Nearly at the same time as Albus, a white, blinding light burst forth from her want. The life size horse reared in the air, and then set off into a full gallop in the air, charging down the dementors that were heading toward them, causing them to scatter and avoid the brilliant white horse. With her wand, she focused on directing the patronus toward the dementors.