You might could do some research on the topic for yourself first, and then pick out what you feel your children could understand at their current ages, and maturity levels.
As you do your research maybe start with these verses from Deutronomy chapter 18
Deu 18:10 There shall not be found among you any one that maketh his son or his daughter to pass through the fire, or that useth divination, or an observer of times, or an enchanter, or a witch,
Deu 18:11 Or a charmer, or a consulter with familiar spirits, or a wizard, or a necromancer.
Deu 18:12 For all that do these things are an abomination unto the LORD: and because of these abominations the LORD thy God doth drive them out from before thee.
Deu 18:13 Thou shalt be perfect with the LORD thy God.
Deu 18:14 For these nations, which thou shalt possess, hearkened unto observers of times, and unto diviners: but as for thee, the LORD thy God hath not suffered thee so to do.
Then combine that with this verse 1 Thessalonians 5:22 Abstain from all appearance of evil.
When we tell our kids that we believe what God has stated clearly already in the Bible then we actively encourage or participate in anything that traces it's roots back to a time when people were doing a lot of things that God said not to do, we are in my personal opinion opening the door to a lot of problems in our lives, the lives of our children and grandchildren and so on.
And I know that people will say that the celebration of Halloween is okay because it has become a part of the culture of America, but no where in the Bible will you find that God says its okay to accept something he has already condemned and even calls an abomination just because all your neighbors, are participating.
I also don't personally agree with the activities a lot of groups including churches have that they claim to be alternatives to Halloween, things like Harvest festivals, or "trunker treat" or any of the other names people call it, even if they tell everyone to dress up as various Bible characters or characters that are not bloody or evil looking.
Whats wrong with the churches celebrating Halloween even if it's in a different way than all their neighbors is the fact being if someone is driving down the road past your church or your home, and do not know what you are doing due to the fact not everyone has any sort of Christian background. Not to mention the possiblity that by encouraging activities on the same day as others are celebrating a pagan day you are in fact by default in a way telling those in the pagan community that there is no real difference between you and them.
There has to be a difference between those who are saved and those who are lost if not there is no reason for Christ to have died. And no merit to the fact that he not only died but rose again on the third day.
A fall festival or harvest day is fine provided it is not done on or near Halloween, and so long as the traditions of Halloween are not followed in any way, because when we copy the world especially on matters that are really spiritual matters for many people we endanger our witness for Christ. In my personal opinion of the matter.
And Halloween is one of the most important days to the pagans, and it's roots come from the druids.
And I have already heard the arguments of it should not be considered any different than any other day, and some want to try to redeem this day in the same way that Christmas has been, the day Christmas is celebrated on was not originally a Christian holiday, I'll let you look all that information up though because I'll type too much, but I will tell you this one of the reasons Christians started celebrating Christmas as they do is so that they would not be considered different from their neighbors who were giving gifts and celebrating, especially since the pentalty for being found to be a Christian was severe)
I don't personally believe that Halloween can be redeeded in the same way because you don't give gifts on halloween, you go from house to house *strangers houses even, and demand a treat, there is nothing positive about Halloween.
I have some very strong opinions about Halloween and a few other holidays because of something that my aunt who was really a witch told me, and because of the research I did afterwards, she told me laughingly, that Christians were dumb because they didn't even know what they were celebrating, then she went into some detail, then I did some research, and now while sometimes I have felt bad because I haven't let my kids go door to door asking for Halloween candy, and have felt bad sometimes when a lot of people in my family have condemned me for not allowing my kids to participate in things that give place in my opinion to evil, I haven't changed my mind.
*Only my two oldest had ever done anything for Halloween, when they went I wasn't fully aware of everything I've learned since the one time they went. Now I don't feel bad that I don't allow it, but sometimes certain ones in my extended family will make me feel bad in a way because they will harp on me that my kids are missing out on various things. (thats what I meant above when I said sometimes I feel bad about not letting them participate)
But if my kids have learned the reasons why Halloween is wrong for Christians, and they then teach that to their children and so on, and it closes some or all of the many doors that are open to the occult in my family just because of all the ones who have dabbled in the occult then that is good. I would like all of my kids to live their lives completely for God, reguardless of who they may meet in life who isn't, and I would also like for them to teach their children one day to live for God.
Closing the door to the occult is harder imo than it is having an open door, I know this because of my own exposure to the occult when I was a child, and I know how even today, that I sometimes will struggle with things that are not of God at all, it causes nothing but problems.
Anyways I know I just said a lot more than I probably should have, but in my opinion you may need to just do your own research and decide what you feel is best to tell your kids at their ages, etc. Because if there is a curriculmn out there on this topic I haven't heard of it at all.
Your best reference in my opinion is to just open your Bible and see what it says on the various things that are often seen during Halloween, and maybe look up what the various traditions of Halloween are, then see if any of those traditions are mentioned in any form in the scriptures and if so was it in a positive light as something we as Christians should be doing or encouraging or was it something God has called an abomination.
There is one Odsyee story that comes on BBN (its a kids radio station) that talks about St, Patrick, that you might find helpful. It doesn't go into a lot of detail, and they usually play that program around St Patrick day, but it is relevent for Halloween to in my personal opinion.
Anyway, hope some of this long post was of a help to you.