L.:
What I would NOT do? Is write my child's name on the OUTSIDE of the backpack. Why? Because anyone can walk to your child and say "Hey! Trey! How are you doing?" The child will not recognize the person - but think they must since they know his/her name!!
Write the name in a permanent marker - like a Sharpie - on the portion of the backpack that goes against your child's back. Or write it on the inside.
Jackets, hats, gloves, etc.? I have a tag that is sewn in - initials - only. So we can easily remove for donation. I have also sewn a specific color of thread into gloves - usually on the wrist portion (gloves) and edge (hats) to aid in identifying them as ours.
Hope this helps!