Those are some good questions. Let me see if I can help a little bit.

First off, during cytokinesis the cells do elongate. I am uncertain as to why that happens, nor could I find any references to address that issue. However, one may argue that elongation of the daughter cells facilitates the separation of the chromosome and organelles. Because microtubules are laid down "end to end" so to speak, their formation results in long tracts upon which are used to draw the cellular constituents apart. That's my guess... As you may have guessed, this story is complicated. Some of them randomly sort out (e.g. mitochondria). Note however, that not all of them seem to sort out. Here's the best summary that I could find:

The nuclear envelope: There is still controversy over whether the nuclear envelope pinches off in prophase to form many small vesicles, which reassemble later during telophase, or whether nuclear envelope proteins, freed from some constraint, laterally diffuse out into the ER, which itself vesiculates. ER and Golgi cisternae vesiculate in most cells.

In telophase, vesicles surround the decondensing chromosomes, perhaps mediated by interaction of lamin B with chromatin. The vesicles fuse to form the nuclear envelope, as the lamina reassembles. Once nuclear pore complexes reassemble, uptake of proteins with nuclear localization signals occurs.

Movement of ER and Golgi membranes along microtubules, mediated by kinesins and dyneins, may re-establish organellar locations in the interphase cell (Golgi near the centrosome, and ER toward the cell periphery).

Many processes in mitosis are regulated by phosphorylation of proteins at the onset of mitosis, and dephosphorylation of proteins in anaphase (to be discussed further).

This info was taken from a web page of an acquaintance of mine. The address is:
http://www.rpi.edu