But if his face reflects the opposite, I always give him the option of going to exchange it for something that he likes more. Then his little eyes begin to shine and the most surprising thing is that, almost always, what he wants is cheaper and less sophisticated.
Even though it isn't always possible, I actually like taking them shopping for a gift and then make a bit of an experience and have some fun with it. It works better for me as I am terrible at keeping surprises :)