Scripture doesn't tell me to go to Church on Sunday*, play chess or eat peanut butter sandwiches, but I do all of those things without worrying that I'm doing something wrong just because it isn't written somewhere.
That said, there are things associated with Halloween that we ought to avoid as Christians. Things like seances, ouija boards, etc. are all things we're told to avoid because of the resemblance they bear to witchcraft and other associated no-nos.
On the other hand, if I dress up as an Imperial Space Marine to hand out candy, or go to a party at the church, that's fine.
Every person must decide for themselves what their conscience tells them in terms of their activities on Halloween, if they participate in any at all. If you find it's spiritually harmful to you to attend a Halloween party or give out candy, then don't. No worries. At the same time, don't come and preach fire and damnation at me if I do choose to.
A few years ago a local shopping mall hosted an event where the various retailers would give out candy to trick-or-treaters. The idea was it would be safer and warmer for the kids. Not a bad idea, IMHO. But the Christian bookstore in that mall chose not to participate... which is fine they didn't have to... but what they also didn't have to do, and shouldn't have done, was to post an employee in the front of the store to sternly scold children who approached the store and lecture them about the evils of Halloween and the sin they were committing. That crossed a line and was highly inappropriate. Not only does it galvanize people against Christians in general, it may have also damaged the faith of some of those kids because now they'll associate Christianity with a mean guy who ruined their trick-or-treating fun one Halloween. If I were the parent of one of those kids I'd have a hard time not knocking that guy's teeth down his throat for talking to my child that way.
*No, it doesn't. Look for yourself.
"He who takes offense when no offense is intended is a fool, and he who takes offense when offense is intended is a greater fool."
"Don't take refuge in the false security of consensus."