I am not in Canada nor have kids. So this is purely my speculation.
Schools in Canada generally start in Aug/Sept. Considering that you are landing in July your kids will have around 1 month to adjust.
You will have 3 option,
1. Bring whole family togather.
I don't find any particular advantage in this situation except all of the family will land togather and clearing customs, etc will be easier
2. Bring your wife only and kids later(a month or 15 days)
Both you and your wife can search for survival jobs.
You'll need to do house hunting, school hunting, etc. Two hands are better than one. Also females are generally good negotiators and would know the requirement of the family better. So will be good for both.
3. Only you land.
You can also negotiate for your wife's job at the same place or try getting her a job so that she can start earning. This will be good if your wife is shy/not familiar with foreign culture/have language problems.
Check the link for child tax benifit. You need to have a PR for getting cctb which won't take lot of time.
http://www.cra-arc.gc.ca/bnfts/cctb/menu-eng.htmlBest of luck for your journey.