Hi Pete!
Sorry, took me a bit to check back, but i looked over your work carefully and made a few thoughts, that hopefully support your great work. as i see you use the same combination as i do. Masscorrections, i mostly tweak on the lowpoly maxmodel. displacement tweaks are fast in photoshop, thats for the finetweaks.
Uncle: i dont think the chin is wrong. just define the jawbone and it will fit. but his mouthpositioning from the profile, could use a slight correction. lay your finger across your lips, from chin to nosetip. this almost builds a line. from sideview, i’d move the lips left, til they almost build a line with the nose.that should also solve the cheeks volume problem. he seems happy. as apaarasited as he is, i don’t think you wanted him to smile 
as for the zbrushsession, don’t overhaste, use (transform) sub- add- / inflat- and smooth-brushes to get bulges and wrinkles exactly placed as supposed to.
Girl (niece): good start so far. my advice for volumeadjustments here are to start with her backhead, place a help primitive, a sphere. with the same amount as lthe loop spline that run vertically over her head from sideview, editmesh, flatten sides. this is a fast controll way to get a head into the right volume. a human backhead almost is spherical.
forehead, is actually too hard falling together, after having tweaked the backhead, you can just pull back the foreheads highest point a bit, less a “shipfrontshape” more a boxy.
if not needed the helpbody anymore, delete it 
Eyes: my advice to easy achieve a fitting eyeline, place a shphere into the “eyehole”. first, it gives you imediately controll over the angles, second, you aswell get the referenceheights that are required to see if the anatomical details are places correctly.
the controllwith of the eylines makes eyewith in between the eyes. the eye is just a spheresegment. lids have mass, so avoid intersections with the reference eyeballs 
best model on a lowpoly model on a lowpoly eyeyball and have a referencecopy of it flipped over the frontal xaxis on 1 subdivision, with an eyeball ref on -x position and as well meshsmove on it (for example right facehalf level0, eyesphere 12 segments radius 1.37cm or whatever left referencecopy with mesh-smove…), to have controll on vertexplacements.
the Procerus (muscle between the eyes, on top of the nose)is too wide yet, about 50%. you can controll it, lay 3 fingers between your eyes 
mouth, same correction as metioned by uncle., in girlscase, move her Larynx, (uhm tube in front neckpart where air and food go trough…) backwards.
lips lower could use a pull down including jav verts, to have same mass like upper lips., and the chin-underlip line is a slight bit short as well. to get ears placed right, i advive you to model them seperately. just close the hole (polymodeling: shift-drag edge, targetweld) select the new faces, detach to object, then, cut n move ear, hide the rest, so its easier to keep the ooverview.not every detail has to have the correct mass, to avoid a too high polycount in zb, keep it low, but make sure, you have all major details cutted, so in zb, you have an easy game to give em the right mass.
Texturing:
Your skinshader so far looks good.
a trick to get texturing fast done is using zbrush with photoshop in combination.
open your displacementmap in photoshop. colorize it. then save as jpg. Import it into texture of zbrush. (i think you already found out about the vertiaclly flipped thing in zb) use projectionmaster and photoshop at the same time. so for largearea things like allover filters or levelcorrections, you can use ps, for seeing exactly what you do and paint microdetails, use zbrush. i found that out and it works quiet fine for me.
for the composition pov, i’d closed a bit up, eventually. to have a playfield to show the expressions on them.
keep it up mate, and don’t overhaste. at the end, just the result counts.
And like steven stahlberg once said: “there is no fast cg. just good cg.” speed doesnt matter at the end. pay all details the attention they deserve.
i hope those sugestions help another crazy viking to send a great creation into the place 
keep on rocking!
cheers:thumbsup:
