I Can't Tell Mom AND Dad

We strongly suspect that our son has NLD, as he exhibits the motor and visual/spacial problems to a very high degree. He basically flunked pre-school because of his poor fine motor skills, supreme inability to cut with scissors, and utter incomprehension of puzzles and legos.  His use of language has always been extremely literal. He insists on   people using proper grammar. My clearest memory of his computer-like mind when he was little is: He was around three and we were working hard on potty-training. One day he ran into the kitchen and had an accident.
I tried not to show my disappointment, but I said, "When you have to go, please tell Mommy and Daddy." He stared at me and burst into violent tears. "How can I tell you AND Daddy? You are in the kitchen and he's in the living room! Am I supposed to run back and forth?" I told him I said the wrong word. Delete "AND" and insert "OR". I meant Mommy OR Daddy. He calmed down.