Hi Annmarie,
A general guideline for snacks on the Disney Dining Plan is any food item less than $4.00. This isn't always the case, but it will help you in finding hearty snacks that can serve as a meal. You may want to consider occasionally using your quick service credits for breakfast just to get a hearty meal at the beginning of your day. I find that if we eat well in the morning, a snack can usually stave off hunger until dinner time.
Of course, most pastries will count as a snack credit, but there are some healthier options as well. At Main Street Bakery in Magic Kingdom you can get a yogurt parfait or fruit salad. At KRNR Snacks in Hollywood Studios you can get a smoothie mad with non-fat yogurt. At All-Star Music and several other resorts you can get a bagel with cream cheese, single-serve cereal w/milk, oatmeal, whole pieces of fruit and power bars.
To get an idea of the many, many foods considered snack options, go to
www.disboards.com. Under Disney Trip Planning Forums, click on the thread titled
Disney Restaurants. Then click on
Disney Dining Plan. Finally, choose
2009 Confirmed Snacks included in the Dining Plan.
Hope this helps. Have a magical vacation!