Assuming the child was born in Canada:
http://www.cra-arc.gc.ca/bnfts/tmtd-eng.html
More info:
http://www.cra-arc.gc.ca/bnfts/menu-eng.html
An application for child benefits will not affect a sponsorship application: Was the child born in Canada? If so, s/he is a CDN citizen. If not born in Canada, see second link above to determine eligibility for benefits.