My philosophies on this are really different than most folks. So you might wanna take this with a grain of salt ...
I (me, myself) would avoid the use of a pre-emergent ... or anything ... a lawn is a decorative and it turns out just great if you just mow it right and
water it right.
In fact, by mowing it tall (3 to 4 inches) it beats out almost all the weeds. And the turf becomes really thick.
So using a pre-emergent would make almost no difference. That just extra money and effort with almost no payback.
As for the manures ... well, that dips into another area of ag philosophy I have that is contrary to what most folks do: I wouldn't want to keep an animal any place long
enough to accumulate enough
poop to make shoveling it worthwhile. Long before that happened, I would move the animals to a new paddock and drag the
shelter to the new paddock too.
So that makes aging the manure, and all of that manure handling stuff moot.