1. China does not recognize dual citizenship; 2. Chinese embassy does not know that you have both Chinese and Canadian passport, so will not actively request you submit your child's Canadian passport for sure.
3. Your Chinese passport will be invalid automatically the day you get your Canadian passport - no need to be cut the corner at all.
4. If you use your Chinese passport after you get your Canadian passport, it is against the Chinese law. -redmaple1(Canada) 2013-9-5