One way to save money on snacks and control the ingredients is to make your own. It may take longer than stopping at the store and buying a box of granola bars but you can control the ingredients and they will be fresher tasting. Some people set aside time (i.e. Sunday afternoon) to prep some meals and snacks for the week. Or if you have time while dinner is cooking during the week to make items ahead of time.
I recently made this recipe for Peanut Butter granola bars and they turned out great. There are numerous recipes available online with different ingredients. Even using this basic recipe, you can change the type of nut butter you use and the flavor of baking chips to add variety. It is also easy to make your own granola to use as cereal or toppings for yogurt/fruit parfaits and other things.
With adult supervision with the use of the stove, this is an easy recipe for children to help with. They can help in choosing the ingredients they want to use.