What scripture says about Halloween and occultism  (emphasis mine)

"Therefore be imitators of God as dear children.  And walk in love, as Christ also has loved us and given Himself for us, an offering and a sacrifice to God for a sweet-smelling aroma.  But fornication and all uncleanness or covetousness, let it not even be named among you, as is fitting for saints; neither filthiness, nor foolish talking, nor coarse jesting, which are not fitting, but rather giving of thanks.  For this you know, that no fornicator, unclean person, nor covetous man, which is an idolater, has any inheritance in the kingdom of Christ and God.  Let no one deceive you with empty words, for because of these things the wrath of God comes upon the sons of disobedience.  Therefore do not be partakers with them.  For you were once darkness, but now you are light in the Lord.  Walk as children of light (for the fruit of the Spirit is in all goodness, righteousness, and truth), finding out what is acceptable to the Lord.  And have no fellowship with the unfruitful works of darkness, but rather expose them."  ~ Ephesians 5:1-11

"Test all things; hold fast what is good. Abstain from every form of evil."  ~ 1 Thessalonians 5:21-22

"Rather, that the things which the Gentiles sacrifice they sacrifice to demons and not to God, and I do not want you to have fellowship with demons.  You cannot drink the cup of the Lord and the cup of demons; you cannot partake of the Lord's table and of the table of demons."  ~ 1 Corinthians 10:20-21 

"[do not] give place to the devil."  ~ Ephesians 4:27

"Now the Spirit expressly says that in latter times some will depart from the faith, giving heed to deceiving spirits and doctrines of demons."  ~ 1 Timothy 4:1 

"Woe to those who call evil good, and good evil; Who put darkness for light, and light for darkness; Who put bitter for sweet, and sweet for bitter!"  ~ Isaiah 5:20

"Abhor what is evil. Cling to what is good."  ~ Romans 12:9

 "Seek good and not evil, that you may live; So the Lord God of hosts will be with you..."  ~ Amos 5:14

It may be tempting for people to think the words "evil" and "demon" too strong for being applicable to playing with Halloween, but from what we've been taught, and from what we've learned and have read through out God's Word - we need to take evil seriously.   It's not a joke.  It's not something to be played with.  I can't encourage you enough to read (or listen to) the materials I've listed below as resources, breaking down the realities of Halloween; and encourage your teens to read and listen to this material to give them a deeper, realistic understanding as well.  Satan would like nothing more than for people to believe that just compromising a little bit on this won't hurt anything...that just a little fun in the dark won't lead to anything...that the children will be just fine...but remember,

"Now the serpent [satan] was more cunning than any beast of the field which the Lord God had made. And he said to the woman, 'Has God indeed said, 'You shall not eat of every tree of the garden'?...Then the serpent said to the woman, 'You will not surely die.'"  ~ Genesis 3:1, 4

I heard a great quote once about playing around with sin or in this case, evil:

"Sin will take you farther than you intended to stray,
keep you longer than you intended to stay,
and cost you more than you ever intended to pay."  (author unknown)

I encourage parents to consider, is it really worth it, playing around with this occultic holiday?