We traded with the Jawas last September. My son is really into Star Wars so we ended up at the Launch Bay 3 times during our trip. They traded with us twice, but would not trade on the last night for some reason. I was thinking maybe they did not have anything to trade because we tried various items and were unsuccessful.
Before our trip, we went to Party City and bought a bunch of small party favors. Bead necklaces, tiny rubix cubes, maracas, a top, etc. We were able to get a bag full of small toys for less than $10 and the 4 kids in our groups had success trading (except the last night, as I mentioned). I even ended up giving a few items away to other kids who had nothing to trade.
Very fun experience and we got some great pictures!