I covered all of the plugs in the house with tape to prevent children from getting electrocuted. Is this good enough? Or should I buy the official plug cover's?
No, I wouldn’t rely on a piece of tape to prevent a curious child from accessing a power outlet. The reason why the certified covers are sometimes tricky to remove or circumvent is exactly to prevent nimble little fingers to do so.
A standard power outlet is not dangerous per se when touched accidentally and superficially, that’s basic safety design. It gets dangerous when little kids start exploring the holes and poking something into them, as they have probably seen the adults do when plugging in something. Unfortunately, most toddlers and small children reach the stage where they enjoy putting pieces together and inside other objects (LEGO duplo, stacking toys...) way before they can understand the dangers of electricity and/or will obey a “don’t touch” rule. A piece of tape will not prevent this kind of experimentation.
I would encourage you to accept the small investment of outlet covers over the possibility of a life-threatening electric shock. Alternatively, install safe outlets that can be used without fiddling with covers.