Sorrel: Sorrel is a fairly common weed in pastures and so long as there is plenty of other forage available, I would not worry about toxicity issues. Reports of livestock toxicity from consuming sorrel are not common.

Many common weeds appear on lists of toxic plants but as is true with much toxicology "the dose makes the poison." Turning hungry animals, unaccustomed to eating sorrel, into a paddock primarily containing sorrel might cause an issue, but a few plants scattered in an otherwise productive pasture won't be an problem.

Oxalate, the compound of concern in sorrel, is also found in high concentrations in spinach, Swiss chard, parsley, and other commonly-eaten foods. Issues do not arise for humans eating these foods so long as they make up a minor part of an otherwise balanced diet. Same holds for livestock.

 I've attached a guide with more details on sorrel. https://wric.ucdavis.edu/information/natural%20areas/wr_R/Rumex_acetosella.pdf 

Chickweed: I found information on palatability of common chickweed: 
Common chickweed has a mild flavor that makes it palatable as a salad herb. It is nutritious fodder for cows, sheep, horses, pigs and chickens, but it may contain toxic levels of nitrate when grown on nitrogen rich soils.

More information can be found here:
https://horticulture.oregonstate.edu/weed/mouseear-chickweed
 https://www.sare.org/publications/manage-weeds-on-your-farm/common-chickweed/#chickweed-ecology

Foxtail: Be sure to get the correct identification on this, Illinois Extension has a video to help with this. 

Has sharp, barbed seed heads that can become lodged in animals' mouths, throats, or digestive tracts, causing irritation. I would look through this publication to confirm your identification: https://www.sare.org/publications/manage-weeds-on-your-farm/foxtails/

These two publications have information on managing foxtail in pastures. 
https://extension.oregonstate.edu/crop-production/pastures-forages/foxtail-control-pastures-hayground
This one from University of California talks about goats being used to manage foxtail. 
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=25578

Thank you so much. I will look over those links tonight. I read the same thing about Foxtails' "sharp, barbed seeds," and this does not seem sharp. Thanks again!