The four you need are:
Frightful Freefall (in Pagoda) - 40,000 studs
Spinning Shuttle Programme (on Apollo Island) - 50,000 studs
Orion's Rockets (in Paradise Sands) - 50,000 studs
Deep Sea Spin (in Festival Square) - 50,000 studs
(Thanks to
Stook85 for the costs)
The large Ferris Wheel is not one of them (I spent ages trying to figure out how to ride it - came to the conclusion that you can't)