Let's do the math......... 1.) You don't know the person who died. 2.)The person's father is someone you think very little of. 3.)Place will be full of JWs, some of whom will make attempts to ahem cough cough "encourage"you. 4.)Your mother might view this is an oppurtunity to ahem cough cough "encourage" you.
Sounds like a no-brainer to me. So when your mother calls again to ask whether you're going, you reply...............