Upvote:2
Notarizing is a relatively cheap and fast process and it confirms that the identity of the person signing it has been verified by a recognized notary.
Your "risk of child abduction" does not seem like a possibility, but if you raise official suspicions for some reason (within your control or not) you could be delayed. Personally, I have never been asked for such a letter in the first place, with a number of opportunities to be asked, but as always YMMV. They are free to make profiling judgments that might not be acceptable in other circumstances.