Son seeing ghost,spirits or something...?

ironically i had just became back interested in the fact that i use to see "ghosts" when i was younger..i haven't seen them since i was a child.. but i wondered if it was just my imagination or not and if someone else had ever experienced what i had.. so anyway my father past a couple of weeks ago and ever since weird things has been going on in this house...my son and nephew point at "nothing" and say that they are scared.. they wont go in certain places when they see whatever they are seeing..and just recently my son kept bugging me that it was something in my fathers old office,he's 3 by the way, so i looked in the office and didn't see anything but he continued to point and wine about what he was seeing....so to comfort him i walked in the direction that he was pointing in and he walked with me and shyly said hi to "nothing" then ran back to me really fast..he doesn't say papa which is what he called my dad so i dont think its him but he does say doctor for some reason...my sister claim that she seen something walk pass her and my mother swears that she seen me walk into my bedroom and close the door.....i dnt know what i should do about it but i hope my sudden interest in ghosts havent conjured something up