Disney Store has Star Wars fleece throws that you can personalize online with your son's name. Also, I think a nice Star Wars water bottle and set of sunglasses would probably come in handy on the trip. New Star Wars shirts or bathing suit (do 6 yo boys still like character bathing suits?), Star Wars beach ball, swim goggles, arm floaties, or dive toys for the pool. I assume they make Star Wars themed sunscreen, bubble bath, and magic towels. Or a Star Wars beach towel. For decoration, I've always thought the Disney Florist luminaries were super neat. You could try making your own Star Wars themed ones by getting lunch size paper bags in black (or whatever color you want-usually you can get colored ones at craft stores) and stencilling or free hand drawing Star Wars shapes (Vader and Yoda heads, some of the simpler ships, etc), use an exacto knife to cut them out, and put a tea light LED candle (bonus points if they change colors) in each bag and set them up all over the room. You could even save the shapes you cut out and use them on a banner or as larger "confetti" sprinkled around the room. I don't know if your son would carry a small bag around the parks for his water bottle and stuff, but you could get a cheap black crossbody backpack (like the Star Tours ones on the Florist site, but plain black from a store) or a cinch sack and sew or iron on Star Wars patches. I've seen small Star Wars fans at Walmart and you can also buy them online, and some of them light up as well. You could buy the Star Wars glow cube/straw clips that they have a at the Disney restaurants from eBay and clip them to a banner or curtains or just have them glowing on the counter, and then he could use them during the trip in his drinks. Right now I see a 3 pack with a Death Star, Millennium Falcon, and X-Fighter with a starting bid of $9.99. Ive seen packs of light up Star Wars latex balloons in the party section of Walmart. Of course, unless you bring a helium tank or get them filled, they won't float. My kids always had just as much fun with non-floating balloons though. You could throw in some Star Wars themed treats. I've seen light up light saber push pop lollipop things at a few stores. I've also seen SW jelly beans, chocolates, pez, and projector pops (project different SW images on the wall and have candy inside).
Edited to add: Obviously, this is a ton of stuff. I know you're looking for something small, I was just trying to give several ideas.
are there any cool light up decorations or toys you've seen? He has several light sabers. 
