[FONT="Comic Sans MS"][COLOR="#300090"]What do you want to achieve with the repairs? Do you want to do a Restoration, perserving the used look and feel of the whole afghan; or do you just want to make it usable again.
For an heirloom restoration, you could "age" the unused yarn you have and then use it to repair the afghan. Crochet a swatch that matches the size, gage, and pattern of the original blanket and launder until it becomes a close match to the piece being repaired. Then frog the swatch and use it to repair the hole. :eyebrow2: (not my choice, but it is what I think would be similar to art restoration reconstruction methods.)
I would just frog the rows with the damage and then replace the full rows. Follow the orignial guage (& hook size) and pattern you used. Then after washing it should match the relaxed original.
Oh, and show them how to bind off a snag to prevent it from unraveling. I suspect that may have contributed to the size of the hole; especially if they simply tried to trim the loose fibers.