Quote:
Family counciling or mediation is definitely in order.
You, the parents, set the overall bounds for your kids. In their own space, grandparents can slightly alter some of the rules that pertain to their space. For example, the grands might allow the kids to make a mess without cleaning everything up when that activity is complete, while YOU may require that they clean up after every activity. Grands may require that they sit at the table while eating, while you allow them to sit in front of the TV. Things that affect overall health or deeply held concerns are set by parents, and should be upheld by all adults who care for the kids. It is fine to have "rules for grandma's house" that are not a complete match with "rules for home." But some universal rules will always apply.
As for telling you how to take care of your chickens, gift them with a small flock of their own, that they may raise as they see fit, but make sure to tell them that you no longer want to hear about what YOU should or should not do in caring for your own flock.
Likewise, you really need to separate their lives from yours. They need outside activities and interests, not to be living as perpetual guests.
If they gave you $17K to convert your basement into an apartment for them to live in, what would you do with it after they move out? Rent the apartment to someone? Convert it back for use by your family? Save it as a place for them to stay when they visit? How you answer that will help guide you to an equitable answer.