My answer is I think a little mechanically simpler and more historically motivated than others, but forgive me if there is too much overlap with other solutions.
I'm going to highlight these two lines you wrote:
Also, lamps bright enough to simulate daylight would be very hard to make.
[...]
Vampires can survive under moonlight and when subjected to a dozen or so candles. Above this level, the brighter it is, the faster they move to avoid it.
I don't think that this first part is too big a deal. Since bright light sources are difficult, but the intensity of the light does not impact the effort the vampires put into opening the coffin, I would just try and harvest power from the opening of the coffin, not the closing.
My suggestion is to attach the hinge to a ratchet, such that the opening motion will drive a gear, but the closing motion will do nothing. This gives you a gear pointing upwards that intermittently rotates a quarter turn in one direction. Because its on a ratchet, its okay if the mechanism keeps rotating (due to other vampires, inertia, etc) because the ratchet will keep the motion from opening the door.
I would recommend using this gear in two ways. One would be to drive a timing mechanism that covers and uncovers a light at the maximum rate a vampire can sustain (remember that it can be relatively dim, so the bare minimum to make it retreat is fine).
The other would be to connect it to a speed reducer. 548
I would also connect the entire bank of vampires to this reducer. Then, I would use that reducer to drive a pump or a lift. Based off of the time period you indicated, it would appear that the primary use for stationary engines would be along the lines of a pump or lift from removing water/materials from mines. ie <PERSON> engine or its precursor the Newcomen engine.
If your vampires will use their arms to push the door open and closed, you could even strap them into the coffins around their chests. That way you could make relatively compact bundles of coffins and time them with a 1/4 offset to get continuous power output from a shaft that runs through the centre of the bundle, and then you could orient the bundle however you wanted. You could use this to drive handcars, etc.
Finally, you said that they never tire, so you may not care about thermodynamic accuracy, but the easiest way to use them if you do decide to would probably just be to burn them, rather than reloading coffins over and over again. 548