In cases like this, where you are not sure if the surviving family will “approve” of your having a Mass said, I don’t even ask them. I simply request the Mass anyway, using one of the many Internet services that provide Masses, I ask them to send the Mass card to me or not send one at all if there’s an option to not send one, and I don’t tell the family.
You having a Mass said for someone is between you and the person for whom you are having the Mass said, and God. It is nobody else’s business. If the person was not religious during their life, then they need the Mass all the more. I’ve had Masses said for celebrities I don’t even know and I don’t call up their families or their agents to tell them I had a Mass said for deceased so-and-so. Just like I said use an Internet service or otherwise keep their name off any public place like the bulletin, so nobody sees it and gets upset.