免税額は個人毎の免税額であって、一家族として合算は出来ませんよ。
Even young children and infants are entitled to a personal exemption. As a parent or guardian, you can make a declaration on behalf of a child as long as the goods you are declaring are for the child's use.
You cannot combine your personal exemptions with those of another person or transfer them to someone else. https://travel.gc.ca/returning/customs/what-you-can-bring-home-to-canada?wbdisable=true