I mentioned that if one gave them to Jews, one would be causing those Jews to benefit from that which was prohibited to benefit, and there would seem to be a problem of Lifnei Iver, putting a stumbling block before the blind.
I would add that this may extend to the giving of the wigs to non-Jews, for perhaps the non-Jews you give the wigs to may later give them to Jews. Why would I think this was a concern? Consider the following mishna and gemara, in the yerushalmi:
נטל ממנה כרכר אסור בהנאה ארג בו את הבגד הבגד אסור בהנאה נתערב באחרים כולן אסורין בהנאה רבי אלעזר אומר יוליך הנייה לים המלך אמרו לו אין פדיון לעבודה זרה
Translation from here.
"The same is the case with a loom made of this wood and with the garment wrought therewith. If such a garment was mixed up with other garments and these again with others the benefit of them all is forbidden. R. Eliezar, however, said: Cast their worth into the salt lake, and he was answered: There is no redemption from idol-worship."
אמר רבי חגיי כד נחתית מן אילפא אשכחית רבי יעקב בר אחא יתיב מקשי נטל הימינה כרכר אסור בהנייה ארג בו את הבגד אסור בהנייה ותנינן ימכר כולו לנכרי חוץ מדמי יין נסך שבו אמר ר' יעקב בר אחא חגיי קשיתא חגיי קיימה מאי כדון תמן אין דרך בני אדם ליקח מן הנכרי ברם הכא דרך בני אדם ליקח בגד מן הנכרי
Rabbi Chaggai said: when I went down from learning I found Rabbi Yaakov bar Acha sitting. I asked, (the Misha states) if you took from it a loom it is forbidden in benefit; if you weaved with it a garment it is forbidden in benefit. (And it continues, if the garment was mixed with others they all are forbidden in benefit.) Yet we learned in a Mishna (about if some wine libations to idolatry fell into a pit of wine) that you should sell it all (the entire contents of the pit) to a gentile minus the cost of the wine libations within it. (Thus, one would not derive benefit from it. So too here, why not say sell all of the garments except for the cost of the forbidden garment within it?!)
Rabbi Yaakov Bar Acha said, Chaggai asked, let Chaggai establish it (the answer).
(Rabbi Chaggai): How so? There (by the wine libations), it is not way of (Jewish) people to purchase wine from a gentile (because of stam yeynam, or yayin nesech), whereas here is is the way of people to purchase clothing from gentiles.
So there is a concern with selling to a gentile things prohibited in benefit to Jews, because Jews might eventually purchase it and come to use it. I would say wigs are more similar to clothing than to wine. (Note however that here we are dealing with a large amount of wine, and clothing. Donating to a non-Jewish charity? A similar concern. Watching to make sure only non-Jews receive them? Perhaps, but maybe the general principle that Chazal established even if in the specific instance one can make sure it does not come to pass (along the lines of Lo plug rabanan). Also, will the non-Jewish child, when he is done with the wig, sell it, or gift it? Perhaps it is only in cases of bulk items, but alternatively there is a problem putting it out into the world where a Jew may eventually come to make use of it.)