Right after deciding to do this, a local grocery store put out an article and recipes on this very topic. This was so timely because I was on the hunt for ideas of healthy little bites to feed them. I have found two of the snacks in the article to be popular with the kids: Individual Baked Oatmeal (I made these in a mini muffin tin and adjusted the baking time down), and Dark Chocolate Cherry No-Bake Bites. We have also tried the Coconut Safari Snack Mix recipe from a Sprout show, which is tasty. Also cheese and crackers, and lightly salted popcorn have seemed fine as well.
The kids are sleeping better and longer with fewer middle of the night wake ups. These results could be attributed to tiredness from going to school, to having the small snack or both. I just like to keep them full and focused, so a little nibble before bed seems to be working for us.