Sims most often get that moodlet when other Sims try to do romantic interactions too soon or repeat the same interaction too many times. Chances are good that Grady was just repeatedly attempting normal interactions with the toddler that weren’t yet allowable if they aren’t considered friends.
However, you also said Grady was eating ice cream and afterwards was looking at the toddler with an odd expression. Did Grady eat Brain Freeze a la Mode? When a Sim sees or interacts with someone who has eaten Brain Freeze a la Mode, they will also get the creeped out moodlet, so that’s another possibility.