I sort of understand the part about "not being sad yet", sometimes death of a loved one doesn't hit people until they've been gone for a while. But...a concert over the services of your grandmother? Obviously based on your father's reactions, you will be at the service. Also, a funeral isn't anything to be feared. The wake...is what can be a little disturbing. A funeral is usually just a religious service, you don't have to see your grandmother, the coffin is closed. And at the wake, you're not obligated to go up to the coffin, and if your family wants you to, go up, close your eyes, pay your respects, and then it's over, you know? Good luck, don't be scared. I am sorry to hear about your loss
my grandma who I was extremely close to (and was a KILLER guitar player...I am serious, classical, so beautiful!), passed away three years ago this coming January, and I miss her so much, it's still "hitting me". But I have her guitars and will soon be restoring them, so it's nice.
Anyway, good luck again, and I'm sorry, once more, to hear about your loss.