So we've been doing that. But even something they enjoy can seem repetitive after a while. So here is how we shook up the norm:
Idea #1: Home made Lunchables. I put crackers, cheese slices, and rolled up slices of ham into a Tupperware, then when they have their lunches the can build their own creations.
Idea #2: Baked-in-a-blanket. I used a package of Pillsbury crescent dough and wrapped the triangles around the ham and cheese before I popped it in the oven. They loved these. I have had requests for more several times.
Idea #3: Kabobs. These were another one they really liked. No bread this time, but I just strung cubes of meat and cheese on toothpicks and filled up the containers. Easy peasey.
How else would you shake up the standard sandwich?