Service dogs and pushy family members

I’m in the process of finding a dog to train as my service dog but a part of me is scared to even find one because of my pushy family members. There’s 4 people in mind that absolutely adores animals, especially dogs. My biggest worry is that they’ll constantly try to distract or take over my service dog while I’m training him/her. I have a cat already that although isn’t the same, they do try to take over his care and have even asked me if they could take my cat because he’s so “well behaved” and “too cute.” They even feed my cat table scraps and dog treats that I specifically tell them not to give him but I get ignored.

I guess what I’m trying to ask is how do I go about having a service dog with family members that will try to take over my dog? Boundaries are almost non existent when it comes to them and animals. I also live in a household that is the main “party spot” for the family so there’s always at least one of them there at my home.