Where did you upload your documents in the first place? Then do something similar in your children's profile. I suppose you can also submit a brand new visitor visa application for the whole family (you, your husband and the children).
How long is your winter holidays? 7 days in Canada is rather short, especially if one wants to visit the country from coast to coast. Besides, there's no such thing as sponsored invite and sponsored letter.
Hope this helps:
https://www.canadavisa.com/canada-immigration-discussion-board/threads/query-regarding-pr-card-renewal-got-prtd-on-h-c-grounds.810509/