From the time our children were small up, until bar/bas mitzva age or so, we made it a point to develop Jewish themes for our family’s Purim costumes, where each of us had an essential role.  We felt that, while there is nothing wrong with a child dressing up as, say, Batman or a baseball player, Purim created an opportunity to have fun in a specifically Jewish way. Weeks in advance of Purim each year, we set to work on a Torah-related costume that called for the participation of everyone in our family of four (we, the parents, and our boy and girl twins).