Hi Nicola,
I think your girls will love the
Kidcot Fun Stops. It is a great way for them to enjoy the countries and maybe learn a fun fact from each country! It isn't necessary to purchase the passport, but they are a unique and relatively inexpensive keepsake of their time exploring different cultures. You can buy the passports at the different Kidcot Fun Stops. I provided the link for you to get more information on the specific locations for each country. In some countries like Morocco, China, or Japan, the cast members will write your child's name in their native writing.
Onto your next question about fun things to buy in Epcot. Here are some of my favorite little finds that I have either purchased or hoped to one day. I love visiting the Puffin's Roost in Norway and seeing all the Viking gear. I once purchased a very small stone troll and I love the Viking helmets with the braids coming out of them! Even if you don't buy anything there, you must get a photo with the larger than life troll statue in the store. In China, I have seen marionette puppets of various animals. Mexico has fun sombreros and colorful maracas. One of my favorite stores is Der Teddybar in Germany with authentic teddy bears and other toys native to Germany. You can often find Snow White or Rapunzel merchandise that is hard to find other places. Also in Germany is the Christmas shop. There you can purchase the pickle ornament, a German tradition. As tradition goes, it is the last ornament hung secretly before Christmas morning by the parent and the child who finds it first on Christmas morning gets a special present from St. Nicholas!
I hope this provided you with some unique options for possible souvenirs. May your girls spend their money wisely all the while creating lasting memories of their one-day (or more) journey around the globe!
~Allison L