Many Christians get bent out of shape about Halloween. Though I see more and more of them relaxing their hardcore views (I was one of them) there always seems to be a contingency of those who think anyone who participates in celebrating is truly rendering worship to evil forces.
It is true that the holiday had a connection to paganism. It is also true that the holiday has a connection to Catholicism. I wont go into the history as there has been a lot already said (just google the history of Halloween).
What I want to address is the issue that we may be unwittingly worshiping the dark forces if this world (and I guess some how giving them more power in doing it). The question is, can a person worship something without knowing it? I believe the obvious answer is no!
To truly worship someone or something there has to be intention behind the action. If thus were not there case then could we not say that nonbelievers could unintentionally be worshiping God?! Of course this would be considered absurd. Worship requires intention.
When children dress up for Halloween and participate in Halloween traditions their intention is not to worship darkness and evil. Their intention is to have fun. There can definitely be other types of worship taking place revealed through costume choice and so on, but an intention to worship darkness and evil is, for the most part, not one of them. Even though there does seem to be an emphasis on scare and gore most of our children choose to dress in what we Christians have come to term as "wholesome" costumes.
Personally I don't see the harm in having a little fun dressing up and meet making. I personally do not celebrate the darker side of Halloween. I would encourage all Christians to do the same, but I don't see the point of completely disassociating ourselves from this holiday that is not seen by the general public as kind of act of worship. That is not the present intention of Halloween.