People have been trick-or-treating for decades, even long before Vatican II, including Catholics. There is no need to worry about it.
True it's been going on for decades but never before in memory have we had so many witches, wiccans and satanists so openly practicing in our midst.
In my neighbourhood was a witch and when her house was sold one bedroom must have been her "prayer"? room and there was a wall to wall pentagram painted on the floor. The SSPX was brought in to bless/exorcise the house and the floor was professionally sanded before the new owners moved in.
Although my grandchildren are too old for trick or treat I think if they were younger I'd be finding an alternative for tonite; church saints party, school sponsored party or get a number of parents to arrange a private house party or drive them around to family and friends and neighbours you know.
P.S. And don't forget the wackos who might lace the treats with drugs.