Hi Shaun, Wilt is the DOF guru and I expect he'll comment, but the cheat sheet you're developing looks to me unnecessarily complex. Lens focal length is not directly relevant to DOF. It's about aperture and framing (well, more correctly magnification of final image). This is because the longer the focal length the further from the subject you need to be to get the same framing, so the DOF works out the same.
Someone on the forum (and I apologise I can't remember who) posted an excellent and easy to remember short list of apertures they use for various framings to ensure necessary bits are in acceptable focus (the values in brackets are the approximate depths of field):
headshot f/8 (7 cm)
Head and shoulders f/5.6 (10 cm)
Waist up f/4 (14 cm)
Above knees up f/2.8 (20 cm)
Below knees up f/2 (28 cm)
Full body f/1.4 (40 cm)
Of course to get two kids in focus you'd have to stop down from these values unless they're both the same distance from the camera. To properly bokeh out the background I understand the rule of thumb is subject-background distance should be at least 3 times subject-camera distance.