two years back, I've renewed twice my parents' visa, the reason is just they like to stay in Canada, they like to visit lots more places in Canada.|
Just don't give the reason that you need them to look after your kids, because then they are taking away a job opportunity that a canadian may obtain.
in one word,Immigration Canada is willing to renew visitors who come to Canada to spend ,not those who come to Canada to take away anything. so try to find any reason you like. you may even ask the agent what reason you should give.