Although your query is addressed to our esteemed senior member "Captain" Qorax, but I am taking this liberty to jump in and answer your question. I was also blessed with a baby boy after I applied for PR.
Now, it is very important that you wait for the passport to arrive...dont send in the documents in chunks, bits and pieces of information can confuse the VO and moreover can delay your file if they keep receiving correspondence from you time and again...
I would do the following if I were in your place (in fact I did the same for myself):-
1) Get brith certificate of child and keep notarized copy ready
2) wait for baby's passport to arrive and get notarized copy of it
3) Make bank draft of CAD $150 towards processing fees for child. This should be payable to the "Receiver General for Canada". Dont forget to mention your UCI number and "processing fees for "CHILD"S NAME" towards canadian permanent residence, child's D.O.B on the reverse of the draft. Enclose Form IMM5620 (Fee Payment Form)
4) Keep ready 5 photos for child as per specifications (dont forget to write his name, D.O.B and date photo taken, your UCI number on the reverse of the photos
5) Make a cover letter explaining the situation
6) Keep ready Additional Family information form duly signed by yourself and your spouse (2 forms required)
7) Enclose Updated IMM008 generic application form
8 ) Enclose supplementary travel details form
9) Enclose Additional dependants form if applicable
10) Enclose certified translations if any document is not in either of the canadian official language
11) Enclose Proof of funds if they have changed (remember you have to declare a higher POF for a 3rd member addition to your family, check www.cic.gc.ca
for that )
12) Put all the above in an envelope and send it to your concerned VO. Do mention your UCI number on top of the envelope !
Hope that helps..