I recently applied for Child Visa for my new born in Delhi, India. The main thing to consider is that you would not be able to apply for Onshore Child Visa as the baby will be on a tourist visa which will have a "No Further Stay" Condition. Bringing the baby on Tourist visa is a hassle. Your child needs to exit the country as soon as the child visa is granted in order to enter on a permanent visa, since it was granted offshore. I am not sure about Pakistan but in India I was able to get the PR approved in just over a month. If you want to go through the Tourist Visa route, You would need to apply for the tourist visa and the Child Visa simultaneously requesting a maximum of 1 year stay for your child. You have a chance of getting a 1 year stay tourist visa since you both have a PR. If the Child Visa is granted offshore prior to that 1 year, your child needs to exit the country and reenter on permanent visa. You may get a continuous 1 year stay or they may give you a visa with just 3 months stay at a time. Your child needs to exit the country if the Child Visa is not granted yet and his/her current stay expires. You might have to exit and enter the country again.
But since you said that you have your PR valid till end of next year, I would advise you to submit a child visa application first and see how long the process takes. You might get it approved fast like it happened for me. If it takes longer than expected, apply for a tourist via stating that you have a pending child visa and you would make sure that the child will exit the country on completion of his/her stay or when the child visa is granted. To avoid the hassle of the child visa and the headaches it may cause, if you have enough time go ahead with the child visa first and decide on the tourist visa later.
Manika,
The child Visa for me from start to end (including Christmas/New Year Break) took just over a month to get approved in India. If all the documents are ready and available to be submitted, it is a very simple process in India. Since you are applying for your visa just now, you will have all the documents ready (Like the police checks for you and your spouse), so you can submit every thing. The only thing which needs to be done for the child is the medicals and it is very simple. You just need the birth certificate, the application forms, DD for the application fee, Passport copies of both the parents, Police checks for both the parents and the medicals for the child. Since yours will be a new visa, I will not recommend Tourist visa.