Sorry if this answer may not be exactly on topic. My question is: how is your intention to renounce your child's Canadian citizenship in his/her best interest ? From what I read, this decision is solely for your best interest- that is to have a possibility to go back to your home country in 10-15 years to look after parents etc.
What is the possibility of having the child born in your home country and having the birth certificate from there and many years later, your child could make the decision to renounce Canadian citizenship and apply for home country citizenship and then go back with all of you. My final comment is that for a child who will grow up in Canada for 15 years, the process to pack up and go back after living in Canada may not be as easy as it seems for you. With no long term link to home country ( except maybe few short holiday visits), it's very hard for kids at age of 15+ to integrate back to home country. Anyway wish you the best, whatever you decide.