Hi Dave, I am sorry for your loss; my own mother will be 90 this year. I know it will be hard when she passes, although it is a good many years.
Read my profile. I was not a JW but my brother had 2 adult children who chose to be JW's. At his Catholic funeral (he died suddenly at 63 yoa); they and their kids, my brother's precious grandkids, stood at the entrance of the church, did not come into the sanctuary and join with the rest of the family. It was so obvious and hurtful.
I didn't say anything to them at the time, because my sister in law was grieving and has done very well at keeping their relationship and accepting their so-called faith. But I learned a lot on this board about their beliefs, and begain emailling my nephew w. questions. I finally got up the nerve to ask him why they did that, and let him know that I was hurt by their actions. He seemed surprised...and answered in typical JW rhetoric, about hoping his dad is at the resurrection. It was obvious that there were many faiths present at his father's funeral, people who cared about him and the family enough that came together to show their love. I wished I hadn't waited so long. I will not hesitate to question any JW who might do such a hurtful thing if anything like this happens again. I think you should question them. You might simply ask why, tell them you missed having them be there for your mom's memory...Then, whatever they reply, let them know that you are aware that their JW teachings probably prevented them from attending. They need to know that We know...they think all their reasons are the best....then remind them that Jesus told us, in Matthew, " Where 2 or more gather in my name, I am there in their midst." It's too bad they just don't get it. Sad. And they call themselves Christians. You don't follow Christ and not live the gospel, esp. at times like funerals, etc.