A person who is myopic, or shortsighted, has blurred vision for distance without glasses. Near vision is clear without glasses.
If we refer to your son, who has RE -1.00D and LE -2.00D, without glasses the right eye sees everything within 1 meter from the eye as being perfectly sharp, and for the left eye things are perfectly sharp if they are within 1/2 meter from the eye. You might like to refer to this blog post about spectacle prescriptions: http://eyesurgerysingapore.blogspot.sg/2014/08/understanding-your-spectacle.html
On the other hand, for the right eye things beyond 1 meter become blurry, and for the left eye things beyond 1/2 meter become blurry without glasses.
So actually your son needs his glasses more for distance rather than near. Having said that, because of the unbalanced prescription, he would probably feel more comfortable if he wore them for reading as well.
Glasses are generally not thought to influence the spectacle power for better or worse. ie they are there to provide clear vision (while worn), and they do not make the spectacle power lower or higher with time.
Myopia does tend to get worse until the late teens, and this progression is associated with insufficient outdoor activity. There are other threads in this forum where I have posted about this.
This is a pretty mild prescription. He may just need them for reading. You will find out once he tries them out. The important thing is that he sees well when reading. Age seven is a critical stage for reading development. Be sure to put his name in the glasses case -- kids lose glasses all the time. Once you determine his glasses use, consider getting a back up pair and be prepared for the fact that he will lose them. If he does, don't be mad or he will resist using them. Good luck!
CBCT -- teacher / librarian
i do apologize it is -1.00 for right and -2.00 for left eye