The real problem is how busy the NEXUS office is where you want to do it, I suspect at Pearson it may take awhile to get an appointment. The thing to do is call and ask, they get cancellations and so on. But I doubt you could do it in 2 weeks, first of all they review your application and then pass it on for the interview to be scheduled.
I was having a chat with the head of the CANPASS office out west the other day and he was explaining to me that there are a lot of quirks with the NEXUS system because
airlines aren't very good at dealing with them. His advice was to carry your passport as well if you have one. Not such a problem with land crossings. The advantage at airports is that you get to skip the line with a NEXUS card. You need to carry your passport anyway if you're going to a third country or a POE that doesn't have NEXUS.
Steve.