Sponsor: A person who is sponsoring in simple words who lives in Canada (in your case your wife)
Applicant: A person who is being sponsored, who is living in Pak (in your case you) Correct me if I am wrong....
Did they mention in the email that who should write this letter applicant or sponsor? From my understanding it should be the applicant so you. But you should confirm that.
So you are saying that you consummated your marriage without ruksati? and your families were okay with this? If so then you need to explain in your letter
why you consummated your marriage without Ruksaty ?
why your families were okay with you both being together without ruksaty?
As you know this is not common in our culture and not approve by our parents usually. Mostly we go though ruksaty and all cultural stuff. As far as I understand you should answer these questions in your letter.
I do not understand the second part of your post “you invited your wife's family ......” why would you send letter to consulate? And why cosulate needs to allow your in laws to come to pak? Why couldn't they come any way ?
I would suggest you to take this opportunity very seriously, you were one of the luckiest once that immigrations have asked to explain your situation. Most of the time they just reject the application without even giving a chance to explain. And then nightmare of appeal process starts. I can say this because I am going through this. I would also suggest you to write a letter in Urdu first and be truthful and honest as much as you possible. Then ask a professional to translate it even though in khi it was impossible for me and my hubby to find a educated translator. Or you can try yourself. Hope it helps let me know if you want to ask anything else.
Thanks