Family reunification category means that ur mother sponsor u to join family in canada...while she was here already waiting for her case to approve and finalized...waiting for u guys to join her in canada...so cic consider it on faster basis for family reunification category...while regular sponship for family class takes little longer or regular time for family to get visa.
So be patient u r in good position to get visa faster...so my advice to u dont panic ...just relax...and watch Cricket 20/20 Worldcup on tv channel..Pakistan is favourite for it any way...Enjoy the Time.. untill u get Visa.
GOOD LUCK