There used to be airlines that provide free airfare if you accompany cargo. If you were to sign up for a trip like that, your mom couldn't go. I had a co-worker that used the program to visit some relatives in England. That was 25 years ago...things were different. I don't even know if they still do it. Just a thought.

You need to go, and go alone, for your own reasons. Your mom would like to go, for whatever reasons. Could you go, and her join you later, after you've made clear your boundaries. The ashes are yours to handle as you desire, but ask yourself, what would your dad be thinking if he were watching your actions and privy to your thoughts right now. Make him proud.