The Kidcot stations are free and fun. Sometimes the CM's will draw a little flag, or a sorta flag. (Like they might draw a Mickey in the colors of the flag, something like that, a rough approximation of the flag.) Other times CM's offered to write a name or greeting in each language.
Some times of year the countries now have free scavenger hunts. They also have some where you can pay money to get a prize.
If you are going now, or very soon, China has merchandise to mark the year of the Rabbit.
At present, the merchandise is a bit limited in many gift shops. Going back many years though, by far, we think the best gift shop is Japan. On our most recent visit though it still looked very empty compared to prior years.
One other aspect of Epcot's WS is it really depends what you have back home, and what you know. For example, someone who lives near the Canadian border probably has access to plenty of Canadian goods. Someone from the Southwest probably has access to plenty of Mexican goods at much lower prices than Epcot. Epcot prices are crazy high compared to Canadian goods bought in Vermont, or Mexican goods sold in California.
One option might be to give your kids a giftcard, and they get to choose how to spend it. Just if you go that route, I advise to do your best to really let them choose what THEY want. If they don't later love what they bought, that is okay.
