I found the aluminum thermoses at Starbucks on clearance for $4.99 (regularly $20!). I got 2 packs of erasers ($1 each at Target), 4 packs of pencils ($1 each at Target), a pack of "Thanks a Latte" thank you cards ($3 at WalMart), 4 mini bags of Millstone coffee ($1.29 each at WalMart), 3 photo-holding pencil boxes ($1 each at Target), and a bag of Lindor assorted truffles (20, on clearance for $4.48 at Target).
I did pencil boxes for Sophie's 2 teachers and Ian's teacher and added their pictures. I already had some yellow tulle, colorful mini paper bags (from Target, I think like $3 for a pack of 12), the colorful raffia ($1 per pack at Target), and the cardboard/metal gift tags (also from Target, don't remember how much, but cheap lol).
I had the kids write their own thank you card messages, and sealed the envelopes with dimensional butterfly stickers I already had (got at Michael's, $1 for 6). Then I wrote my own cards to the teachers and principal as well.
I put the erasers and pencils (sharpened and ready for next year!) inside the thermoses. The coffee and truffles went inside the paper bags, which I stamped with a little stamp I already had. I punched holes in the bags and in the corner of the card envelope (not through the cards themselves) and tied those on with the raffia. I stuck the thermoses into the pencil boxes and put the yellow tulle around the edges. The cardboard tags worked perfectly on the thermos lids and let them know there are more goodies inside!