My condolences for the loss of your mother. I lost my mother two and a half years ago and it was the most difficult thing I ever went through, so I understand what you're going through and I certainly respect your request.
I spoke with our executive director about this, though, and we're in agreement: unfortunately, we don't think it would be appropriate for someone to be carrying human remains on the con floor. We think that it would make a lot of people uncomfortable to know that someone was carrying them around. (I, for one, get the heebie jeebies around human remains--even those of my own loved ones.)
We have some ancillary concerns about the potential for damage to the urn; the potential of the ashes being scattered, necessitating extraordinary cleanup measures; the potential for loss of the urn; etc. These may be extremely unlikely, but they're still something we need to take into consideration. And unfortunately any one of these issues would make us leery of saying yes.
But mostly, it came down to how we thought people would feel about being around human remains at the convention. Though for you this is a way to share something special with your departed mother, it's unlikely that everyone would feel the way you do about it.
Though we would ask that you not bring your mother's ashes on the convention floor, we wouldn't have an issue if you brought them to the convention and left them in your hotel room. While this may not be sharing the convention with your mother in the way you had hoped, I hope it would still allow you to share it with her in a meaningful way.
