A skill challenge for scouting and gathering information sounds decent - streetwise, history, diplomacy, nature, perception, even thievery can all apply. Basically as a 'New to town and getting to know things'
And each success could earn a little more information, and they're tapped out if they end up failing. Information or Irontooth, what the keep used to be used for, what things in town people care about and want help with, etc.