Batteries in Products Manufactured in China

Does anyone have an opinion about whether to have my Chinese manufacturer include batteries in my electronic novelty item? I will be selling the product on Amazon and possibly Ebay. Some similar items come with batteries; others don't and the end customer is expected to supply their own. I'm not certain about the quality of the batteries that the manufacturer will put into my product, but it would be far too labor intensive and costly to insert my own batteries before shipping to the end user, and it would be nice for the end customer to receive something that can immediately be played. Having said that, I'd hate for the end customer to receive a product with defective batteries in it (especially after I would have advertise "batteries included".

Any advice or opinions are welcome.