At older times, no child would have an interest to enter the garage area unless he dreamt of becoming an auto mechanic. These days, garages are filled with many things, which may attract their attention and they have become parts of the main house, where people engage in different activities. On the other hand, they can be dangerous places for little kids, who cannot understand the dangers of sharp objects and the power of garage door parts but restricting the area would only intrigue their curiosity more. The solution is to improve the conditions and make sure that the mechanism is safe and will not provoke any accidents.
You need to lock away the sharp tools and chemicals. Motor oils and lubricants for the garage doors must be kept out of their reach as well as the remote controls. Children would love playing with remotes and the moving door but these games can be dangerous. Damaged sensors and weak springs may lead to serious accidents and this is why you must teach kids the threats and don't let them run back and forward under the open or closing door.
Keep the garage door clean and well maintained