Since there are a lot of different ways to solve the main missions, I won't give an in-depth description on how to do so, just what needs to be done and a simple description of the solution. Some of the mission tasks that characters give you can not be completed all at once, but you will notice when a character is available while you play. This also goes for some of the bonus missions.
Some bonus missions, like the pigeons and the unique jumps, can not be completed until you have unlocked all islands.
Good luck and have fun playing!