without example images, it's hard to give good feed back :)

I guess my immediate thought about "quality of light" is that softness comes from large sources at close range - if you are using the umbrellas at a distance they would easliy become "harder light sources"... which you might not like the look of (?)

on the other hand, having a bright (and big) source close to the center subject will result in super-rapid fall off in intensity (r-squared stuff) as the distance to the flash increases...

so moving your strobes light further away from the group would help with that (?)

the other thought is to do some test shots on your own and see where you need to position these lights to get the coverage / quality of light you want :)