You need to apply Visitor visa. Don't worry about validity. You will get validity as per your husband's work permit record end date.
Make sure you fill the below details in IMM5257e form,
Purpose of my visit - a) "Other" b) "Accompanying parent"
2) Indicate how long you plan to stay From : ( Any date probably the date you planning to travel) To: (Your husband's work permit end date)
