The IRS implemented a facial recognition system for their online taxpayer account system, but has backed off it. (See IRS announces transition away from use of third-party ...) There are no current plans to use it for efiling, so at least for now there is no need to worry. I would imagine the IRS would have to address concerns like yours if they do start requiring additional identification, but as a parent you are a responsible party for your children's affairs.
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