ashley white , 30 , and paul thomas , 32 , charged with child abuse and neglect .
couple 's son , noah thomas , 5 , from dublin , virginia , was last seen alive march 22 .
mother went back to sleep , child was missing at 10 am when she woke up .
after fbi search , noah 's body was found in septic tank on family 's property five days later .
thomas and white 's 6-month-old daughter was removed from home a day later .