Complex sentence: Newer, more advanced rides do not usually start as soon as coins are inserted; instead they prompt the rider, parent or guardian to press a start button, so as to allow the rider to seat him/herself comfortably before commencing the ride.
Split into simpler sentences: Newer, more advanced rides usually do not start as soon as coins are inserted, instead prompting the rider, parent or guardian to press a start button. This is to provide time for the rider to seat him/herself comfortably before commencing the ride.