We need first to understand and explain to our children the origin of Halloween before making or allowing them take part in it. It is after all an un Islamic habit based on a story which does not support Islamic noble values.
If you take is as a cultural practice only and share it with your non Muslim friends or colleagues, it might be accepted by some scholars, but you must be sure that your children should not take a wrong message from participating in such cultural events.

'Living among non Muslims does not mean that we have to adopt all their customs and habits. We take the useful things which do not contradict with our religion, and avoid harmful things.

Wassalam.