Yes, if your family returns to Canada and establishes residence by joining school, getting a job etc, it is a good indication of your intent to return. But all that will be moot if you don't answer the letter. You need to write an explanation and show concrete steps that you have taken already - you can't reply and say "We will move eventually".
If you are able to send your family back before the 30-day deadline (and your kids start school), that will be a good response. You can then reply - "We were intending to return as soon as I got my PR, but I understand that our intention may not have been clear. However, since receipt of this letter, my wife and child(ren) have returned to Canada and have started going to school. I plan to join them as soon as I get my PR".. or words to that effect.
Thanks a lot bro much appreciated and do you know how long does it take from the time I reply until I get a decision ?