This is a big big NO! - as all the agents are probably going to say that. The owners are strongly advised not to be present during showings for various reasons: one of them is that the owners are emotionally attached to their home. They will probably start talking to potential buyers pointing out things that they think are important or good for them but may not be that important or good to the buyers. It is better to leave the showing to a professional, who knows the selling points are and what things they should not point out, etc., and who does not have emotional connection to the house.
I read somewhere that if the owner has to sell but is not happy with this fact they may even unconsciously sabotage the sale, lets say start cooking smelly dishes or say something in front of the sellers that would scare them off. It is really better not to be present at the showing, provided that you are confident and comfortable with your agent.