Other people will come by with more advice, but my initial thought would be that IF you decide to go this route, definitely apply for a visitor visa for your wife in advance. They'd be perfectly within their rights to deny your wife entry to the UK, as she's not really visiting. Risking getting a holiday visa at the border would be incredibly foolhardy.
But who knows, she might be granted a visitor visa if you apply in advance, and then, yes, you could go forward with this plan.
Other things to think about: I think it can be quite difficult to get a school place in England, so your girls might not be able to start right away. You'll still need to meet the financial requirements to sponsor your wife, as you mentioned, but some of the routes require you having the job for 6 months before sponsoring, so check out the details.