When building new roller coasters, keep the station level with the tops of the cliffs whenever it is possible. Choose a mixture of cheap (e.g. Wooden Side-Friction, Steel Mini) and maneuverable (e.g. Wooden Twister, Steel Corkscrew) coasters when developing your park. Once you have a decent amount of rides, consider adding a Chairlift to connect the sections of the canyon. So long as you continually expand the park without running out of money, you should find this scenario much easier to complete than what it appears to be.