Is your friends mom a witch? Seems like sharing handled it fairly well.Her mom has salted and burned the carcasses, and I've suggested protection spells and jars. I'm still new to witchcraft, so I want to make sure we'll be able to do the best to get rid of any possible curse they might be getting. Any tips or ideas?
Since the carcasses were placed in your land, in the open, I'm assuming the curse (if any) is directed at their property and home. I would also make an offering to the spirits if the land that you live on, and do a cleansing ritual on your friends property.
Also, make sure all the rent/mortgage/property taxes are paid and up to date, if this is the case.