advice please

im kind of stuck in a situation where my MIL wants my husbands step father to be called grandpa which im really not comfortable with. my dad passed away when i was 11 and i really only want my children to know who their real grandparents are, she was talking to me today about it saying "i like my grandkids to call him grandpa out of respect, hes not a bad person blah blah" and its not that i dont like him or think badly of him its just the way i want to raise my children. and its quite hypocritical of me if i allow it because ive already told my mum that her husband will just be called by his name and my husbands step mother will just be called by her name. ive asked my husband to speak to her and tell her that we don't want him to be called grandpa but he keeps avoiding the conversation. anyone else have this problem? its giving me so much anxiety the closer i get to my due date.. edit- my husband completely agrees with me and doesnt want step parents to be called grandma or grandpa etc but he hates conflict which is why i think hes avoiding the conversation, it isnt just my views. we completely agreed on it together.