Finish the Wooden Roller Coaster first, as it is the least maneuverable. Build some small attractions, add necessities, hire staff, and open the park. Then, start building the other roller coasters. They can be as short as you want. Note that two of them allow a launched start, which can save you a lot of room!
Also, remember that guests will need some space. Expand pathways to unused areas of the park and build more rides there to prevent crowding.
Or you can just forget about the guests, max out the loan, and complete this scenario fairly quickly.