M80: I would Ta’anah that the custom of many to wear full customs on Purim nowadays as actually taken from the Goyim by Halloween.
There is no Avodah and no celebration in kids asking for candy. It’s not a religious service at all. In fact, most kids going out and asking for candy probably aren’t religious anyway. There should be nothing Assur about giving them the candy unless you are worried about Lo Sechonem.