You'll need to contact CRA and find out if any of this lump sum related to the UCCB (Universal Child Care Benefit). If "yes" then you should receive an RC62 slip and it will need to be reported on your tax return.
If the amount you received is only for Canada Child Benefit (CCB), then you will not need to report anything on your tax return.
You can contact CRA General Enquiries at 1-800-959-8281