'AND YOU CAN BRING ME -': Main attraction, of course, at the Christmas Open House held by the sisters and staff of St. Joseph's Mercy Hospital for children patients was the man with the white whiskers and the deep laugh. Some of the party-goers able to attend the affair in the hospital auditorium are clustered around Santa Claus and, presumably, the little fellow on Santa's knee is only about half-way through his Christmas list. In the evening, staff members presented a program of entertainment for child and adult patients from the auditorium stage.