There's a post about this in the [link] 'Harringay Steam Train Watchers' group, but unless you are signed up to the group (how to do so is here) you won't get an alert about a new post there. Something a bit different for a brief family outing, given the relatively friendly timing? A good place to view is from the 'up' (towards London) platform.
Sat 8 Dec about 0915, Duchess of Sutherland with the Lindum Fayre excursion to the Lincoln Christmas Market. Tour details here, live times here. The engine is newly back from overhaul and now carries the striking LMS red livery, not the previous BR green as in the tour details photo.