I did the exact same thing as you are asking about, adn I'm currently in Toronto with my husand and 2 kids.
- You apply for all visas/permits together.
- Purpose of travel, you basically have to show you are planning to return to your home country once your permit is over. Show ties to homeland, for example properties you have, or a letter from your employer, in case you are an license. nd that your purpose is acompanying your wife dring her studies.
- Your kids need a visa tu get in. Kindergarten (for 4 year old) is enough with a turist visa. For the 10 year old, I'm almost sure you'll need a study permit. Doule check on the cic website, just in case.
- No letter of acceptance for your kids, specially if they are going to public schools. At least I did not have to sho any and have a 4.5 (kinder) and a 2 year (in da care)