Can anyone help me translating a letter from english to spanish?

My grandma is sick, like really sick, in Mexico and my dads going to see her this weekend and wanted me to write something to her, but the thing is I don’t want my horrible choppy spanish, I want it perfect, but I do not want to ask my dad for help we do not have the strongest relationship, so if someone can help me translate what I have written in english it would mean the world to me:

Dear grandma,
My dad tells me you’re very sick and I’m really sorry I can’t be there with you. I know I havent been the best grandson, I haven’t called and I havent been to Mexico in some time, but I still love you very much. I want you to know that I promise I will be there soon to spend some time with you now that I’m older now, and probably understand you better. I miss you so much and I can not wait to see you soon.
Love Joel