A few other things I do:
1. I write notes on their napkins every single day (and draw a few little pictures too!).
2. I pop popcorn for a little crunch.
3. I cut out shapes in their sandwiches that correspond to the season (hearts for Valentine's Day, pumpkins for Halloween, trees for Christmas, etc).
4. I let them make their own trail mix blend on the bulk nut aisle of our grocery store and then we bag it up for their snack at school (they like that they have their own special blend).
5. I sometimes use Nutella or vanilla almond butter for a little change on their sandwich.