I understand the confusion and it could be "gray area" (assuming YOU meet that criteria, even if your son doesn't). But if I remember correctly, the way I read the law it is allowed.
At any rate, this has been around since 2014 and I have never heard of the IRS denying doing it that way. In other words, so far it has been okay with the IRS.
I would allocate 100% to your son and get the larger credit. In the unlikely event the IRS changes its viewpoint of the matter and were to challenge you on it, you could just amend and allocate 100% to yourself (which is what you originally were going to do anyway).
