@silverden: And being taught how to make potions, which is the real reward he's after.
Given how this grandma has been, it wouldn't surprise me if all 3 quests are actual tests she had in mind for him, and the receptionist girl only pretended to remember and ask about the 3rd one.
Help the old man with the massive bricks for little gain (hard work for almost no reward)
Play with the children (judge of how he handle the weak)
Help the monkey (will he accept the shame of 'failure' to help Doni out)
Maybe she wouldn't outright 'fail' him if he refuse the monkey quest, but she'll likely teach him less than what she'll be teaching now that he not only accepted the monkey quest, but took it one step further and helped him win and thus get to tell the lord his thought.