Purely observation of customers that age group coming into my shop, decals and stickers for laptops/tablets and water bottles are top sellers! That age group seems to be into "Space Stuff". You could get a pack of stickers and a Nalgene for them to decorate and put a bunch of gift cards and fun foreign candies/snacks in the Nalgene water bottle almost like a stocking stuffer.
I think for boys ( if they like sports) balls, hats, T-shirts, water bottles. If they like videos games a gift card is a good idea. If they like basketball a small basketball hoop for their room.