Let me state that I live in a brand new home....in a field that no other homes have been built on..and yeah....we have what we call visitors at times..you may call them spirits,etc....
My oldest has picked up on them and when she does she tends not to want to go upstairs by herself
If this is the case with your kids...the power of prayer and asking for God's help is awesome....Whenever we have a visitor..I ask God to please have whomever, whatever to take the visitor to the place that they need to be and ask for protection of my family.
My oldest is 6....and talking about spirits and visitors might not be good at this point in time..but telling her to ask for God's help and protection and to let her know that God loves her will hopefully calm her fears.
Sometimes having spirits can be a joy, especially when loved ones have passed on and give you that special good by..and others...well you don't know who or what they are and it's best to put it in God's hands.
Hope that helps. Feel free to contact me if you'd like.