I suggest you apply outland about 6 months before you intend to retire, though you can look at the forums closer to that date to see how the processing times for an application from the UK are going. Your wife will have to show proof of intent to return to Canada, so she could show things like the house you have bought or will still be looking for, your plans to retire, her plans to quit her job and look for a new one in Canada, etc.
You can come to Canada as a visitor before the PR application is finished processing, so if it is not done by the time you retire, you can just come to Canada like any other visitor from the UK.
Once you are a PR, you can work at any job a Canadian citizen could (except for a few that require high security clearances).