If your son is a minor, a permanent resident and lives with you, he will become a USC when the first one of you takes the oath of citizenship.
You can apply to get him a passport immediately after you (or your spouse, or both) get your naturalization certificate (by the way, even though they don't ask for it on the passport form/instructions, include your marriage certificate in your son's passport application - they came back to us during the processing and asked us to send it).
However, I believe that you cannot apply for two passports at the same time with a single naturalization certificate.
You can also fill in an N-600 right after your oath ceremony. That application takes a copy of your naturalization certificate, making life a little easier. N-600 processing takes a long time (late June, 2006 until now, so far). It also costs a couple of hundred dollars. The advantage is that your son gets a permanent "Citizenship Certificate" (unlike a passport that expires).
N-600s are much easier to fill out than N-400s - it should be easy for you.
Good luck