My wish is to wake up tomorrow morning looking like Elizabeth Taylor, circa 1952. However, as disappointed as I am, I recognize that probably is not going to happen. Wanting something is not the same as being able to guarantee that something.
Also, nobody is entitled to a gift or the fulfillment of a wish, no matter how deserving that person is, or, for that matter, however much someone else wants to gratify that wish.
Weeble wobble, I don't think you ruined the child's Christmas at all. Rather, I think you gave him an even better gift: the chance to mature and realize that you just can't get everything you want. I think he's very fortunate that someone cared enough to choose his ornament at all and tried to give him something, especially when you went through the effort, care and expense to provide him with thoughtful gifts that were within your ability to provide. I'm guessing there were other ornaments on that tree that weren't chosen at all because there simply were no takers.
I'm sure the little boy might be disappointed to not get that Kindle he wanted. But then again, I think he'll also get over it. We all have to.
I didn't get that pony I wanted from my parents when I was five. I survived. He will, too. And, just because he didn't get that Kindle he wants this Christmas, it doesn't mean that he will never get one. It just means that every whim we have can't possibly gratified every moment we have them. It's character development - and that's the gift that keeps on giving.
Don't feel bad at all. You did a good thing. Blessings to you for your kindness and generosity in action and thought this season.