Double check with the teacher/school about if a refrigerator is available; probably not a big deal for a three hour day, but it is nice to sometimes send multiple days at a time if you need to.

Also ask how they want it "packaged" our preschool wanted one big bowl of fruit so they could practice family style eating - passing, scooping, etc. While I know others need to send individual servings of snack.

We went four or five days a week and took snack each day for a week. I tried to mix it up - cheese, fruit, veggie, cracker. My kids always liked bringing the random "trail mix" which was usually raisins, dried cereal, and whatever else I had in the house.