I have a few of those children myself. I have found that asking them to make a list of what they want (can be formatted as a letter to Santa for younger kids) works well. Then you can have an idea of what to get them. You'll have a list of what they like and want. Choose from that. Be sure to tell them that this is a "Wish List" and they may not get everything they write on it, but be sure to encourage them to make a realistic list with plenty of choices. That way you'll know that you are getting them what they like, and you still have the element of suprise on your side because although they have an idea what they are getting, they won't know exactly.

You can have them make out their lists during the THanksgiving holidays or even earlier depending on your shopping habits.