Look at it as if you were at wal-mart and one of the cashiers asked you to leave or a greeter, they are employees not an agent of the owner such as a manager or a department head who can speak directly for corporate. The same thing goes for elsewhere, if I am at a persons house for a get together and they have a friend come and ask me to leave I am still going to want to hear it from the owners mouth not some lackey that does not know the law.
I am going to be in the same boat in the next week or so, I have a kids birthday party to attend after the OC meet in clayton on the 10th, the house is right down the road. Alot of my fiancee's family are anti gun but some of them whose house we are going to are not as far as I know. However I can see one of the other relatives coming up and telling me I cannot have my gun on around the kids. Too which I am going to go ask her cousin who is a detective and firm believer in the second amendment, if I can have my firearm there if not then I will bid them good day and me, my fiancee, and my daughter will leave, simple as that.
Basically rule of thumb would be ask for the highest person up the ladder you can get whether it be in wal-mart, church, or a friends house and make sure you get a straight answer from someone in charge not someone who thinks they can speak for someone else. hope this helps.