The thing with a visitor visa (even if you're approved) is that it is for visitors - not for people who want to move to Canada. A visitor visa doesn't let you stay in Canada long term and if you come as a visitor, you're going to find it very difficult to change your status to something long term (i.e. sooner or later it's extremely probable you're going to have to go home). While here on a visitor visa, you won't be able to work, your daughers won't be allowed to attend school and none of you will qualify for free health care. If you want to live in Canada (i.e. become a permanent resident with your daughters), then by all means try for a study permit first or a work permit. In my opinion this is a far better choice than the visitor visa. If neither of these work out, then you'll need to find a way to qualify under one of the immigration programs listed in the link provided earlier.
Regardless of what you do, I think it's very important that you return to Nigeria and re-establish yourself there for a number of months (again, I would say 6+) so that you can demonstrate ties to your home country when applying for the study or work permit. To qualify for a work permit, you'll need to find an employer in Canada who is willing to offer you a job and can obtain an approved labour market opinion. To qualify for a study permit, you will need to be accepted by a school in Canada first. Note that it's too late to join the September term - so you would be looking at January at the earliest. The education path you select in Canada must make sense in light of your previous schooling and experience. Assuming you have a BA in Psychology - it would make sense for you to be taking a Masters in Canada.
Regardless of what you do, I think it's very important that you return to Nigeria and re-establish yourself there for a number of months (again, I would say 6+) so that you can demonstrate ties to your home country when applying for the study or work permit. To qualify for a work permit, you'll need to find an employer in Canada who is willing to offer you a job and can obtain an approved labour market opinion. To qualify for a study permit, you will need to be accepted by a school in Canada first. Note that it's too late to join the September term - so you would be looking at January at the earliest. The education path you select in Canada must make sense in light of your previous schooling and experience. Assuming you have a BA in Psychology - it would make sense for you to be taking a Masters in Canada.