A snack can be a real food
A snack can be fruit, bread, yogurt if milk is fine, or leftovers from lunch. It does not have to be a separate category of food.
Snacks can look like meals
When snacks look like meals, dinner is less of a shock. The same foods show up, so the day feels like one kitchen.
Leftover rice, a piece of fruit, or a small bowl of what lunch was are all snacks. A special snack aisle is optional.
Yogurt only when milk is fine
Yogurt is a milk food. If milk is an allergy, yogurt stays off the snack and off the plate. Fruit or a safe leftover takes that place.
If wheat is an allergy, bread and oats stay off the snack too. Use the food they already eat that fits.
Sit for the snack
A snack in a moving car, or while walking, is harder to supervise. Sit when you can, especially with anything soft that still needs chewing.
Stay with them while they eat. That is the safety piece, whatever the food is.
A sentence you can say
“This is the rice from lunch.”