Stacey, so sorry to hear that big
I have not read the replies, but you should do what you think best for you.
This is a time to support family & get support, I take it it is your mums dad & I can understand why she want you there, for support for her & for you to say goodbye. She has probably been in this position before & saying goodbye to a loved one has helped.It also helps with the grief process.
Bad memories fade, death, funerals they all fade to a acceptable state, but the love & fun shared never does.
We don't always get a chance to say goodbye.
Best wishers to you & your family at this sad time.