Avoid thick areas, steep climbs, and stream crossing where there is no bridge. Kids especially need the reward of finding many control markers at close intervals to hold their attention. Courses beyond the easiest get both longer and more difficult. Overall length is longer and distance from control to control is generally longer. Less obvious features are used a control points.
More route choice exists between most points.
After you have designed your courses on paper, always walk thru them with the map. Hanging pieces of engineer tape at each control point location to ease setting out the points on the actual event day. Check again for map errors. They stressed that every situation is different. A checklist of equipment will help at the event planning stage.