although implied, it isn't clear from the posting if you are attempting to receive derivative status based on your wife's CP. if you are, and if your wife's CP is denied then AP may be irrelevant as the grounds for denial are fairly serious (fraud, deception, medical issues) and may make you inadmissible even with non-immigrant status or AP.
another concern would be the requirement for additional documentation. if additional documentation required travel back to the US or required a period of time to acquire then it would mean considerable inconvenience to yourself as you have no status (no status that allows work that is) to re-enter the US with. for this reason i would think there is sufficient motive to delay the interview or do everything possible to receive AP before the trip if there is any doubt about your documentation (there are previous postings showing required documents in this thread). maybe another poster in this forum can share any experiences involving changing interview dates.
on a positive note, my wife and i completed our CP in montreal. we found the consulate staff to be polite, professional, and very straight forward.