For my college kids whose quilts I don't want to be stolen, I hand embroider their names in the borders on the quilt - left side, center or right side corner. I also put quilt by my name plus the year it was quilted. Things were frequently stolen in their dorms if they left their rooms without locking the doors but their quilts were never bothered as their names were on them large enough that no one would miss the fact that if they stole that quilt, they couldn't use it and to rip out my stitching would have left a visible imprint behind.
For the quilts I'm not concerned about being stolen, I use the embroidery alphabet on my sewing machine to make a label on a separate piece of fabric which I then fold and hand stitch in place. In this instance, if you do that, I recommend you machine stitch it in place because you don't want to risk the label coming loose. Machine stitching definitely holds longer and better than hand stitching for these things. In my case, I see my family recipients and would reattach the labels should the need arise. Hopefully his quilt will be able to travel with him where ever he goes since you are making it special for him. It would be a real shame for them to leave that quilt behind with the foster parents as the boy will need it.