CS7. Straight through. Stockwell is daft, Oval a bit less dangerous than it used to be. Just keep on through E&C & up Borough High St. Not a difficult route. Quite a bit of bus lane.
It will probably be a bit of a shock, but there will be a lot of other cyclists about. Holding the line is important.
Maybe they could ride in with me one time, and I can show them the issues and how to get round them.