to be honest I can see both sides of this, on the one hand the earlier they see this, have it explained to them then chances are they will be better able to handle this kind of event later in life, at the same time why should they go when it's not someone they knew (that may make it easier), as for his wishes, fair enough but he's dead. If he goes to the service he doesn't have to go them tipping him in a hole. If you sat at the back he wouldn't see that much and would probably get bored if he did get upset you could take him out the back. Either way you can't win on this.