Ok, what I would do is get the first dress, since it seems to be your favored one, close to the way you want it fit prior to the sitting.  Convert it to a prop.  Open it in UVM and group the coller and the bottom hem together with their respective main cloth groups and save.  Import it into poser welding verts and then it sounds like it should go through the cloth sim from the current pose animated to the full sitting.

Laces, I agree are a tough cookie to deal with well in the cloth room.  They tend to collapse and get seriously smurfed up.