Denise,
At one time none of the CityWalk restaurants (with the exception of Emeril's) took reservations, but I think that's changed. Some take regular reservations and others offer Priority Seating (like Disney).
Click here to make an online PS at HRC up to 30 days in advance.
It's not always necessary to make reservations in advance. It really depends on what time of year you'll be there, the time of day you want to eat and the popularity of the individual restaurant. We eat at HRC most trips and we've always been seated straight away. However, we tend to visit during slower times and we always eat there for lunch, never dinner.
We've never had a problem getting into a Disney restaurant either, but for those we really want to do, we usually make a PS to be on the safe side. We prefer not to make too many because we like to keep plenty of flexibility in our plans. There are very few restaurants for which reservations as far in advance as possible are essential. Victoria & Albert's at Disney and Emeril's and Tchoup Chop at Universal are the ones which spring readily to mind. Others we have booked in advance are California Grill, Jiko and Boma, but we've also eaten at all three either by booking at very short notice (the day before, or the day itself) or as walk-ups. Cinderella's Castle for breakfast is notoriously difficult to secure, but I doubt your 13 year old son will be too bothered!
Are you looking for recommendations? If so, when will you be travelling, where are you staying and what plans do you have/which parks will you be visiting?