Remember that a Christmas gift doesn't have to be perfect! Is anybody going to shoot you because it isn't exactly right? No! It just has to say, "I love you... Merry Christmas!" For the grownups, think what each adult likes to do, and find something that fits the category. For the children... it depends how much you want to spoil them! :^) But young children don't care how fancy or expensive a gift is as long as they can play with it! And books can be very nice gifts as well.
I get overwhelmed, too. I love to look in the stores and the catalogues, but it's a sensory overload for me rather quickly. I deal with it by saying, "THAT'S the gift!" and having done with it. I try to decide as quickly as I can without impulse-buying. It helps! Give it a try. You don't have to go for perfect; just go for enjoyment.
If the towels your sister gave were monogrammed, I'd take towels for a present!