My mother-in-law made me ask this question to the minister who officiated for my wife and I. She said it was the normal thing to do. I said “I am paying him AND I have to feed him?” She said “Yes! It is tradition” So I invited him. He never showed up. If I only knew then what I know now. Anyway, if your Mother-in-law makes you do this, let her know that tradition is old-school, and “Thank you kindly for the offer, but no thank you.” I do enjoy this work, but I also enjoy my evenings with friends and family