I went to the funeral of both my father grandparents and my grandfather on the other side of the family. I don't remember those situation as being extremely traumatic or unpleasent. My younger sister, sat the age of 4 really insisted on going to my grandfather funeral and she were one of the most positive people there.
I think a lot of it has to do with the parents approach to death and how they explain the situation to the child. I think that if this is the first time your child face the notion of death then without any explanation, this can be a very confusing situation, but if this comes with explanation before hand, and some talks about the meaning of the evednt and the child's feeling - this can be a good experience.
I think the best thing to do is to explain the kid what's a funeral and how it's going to be and what's going to happened and go over all the information you have about it with the, and then askk them if they want to go or not.