Check the menus on allears.net. They have the little purple snack logo next to eligible items. The Disney website is misleading because when it says "no dining plans" it means only that you can't get a meal there. However, many snack only places take dining plan snack credits. Disney should really change the wording because it's confusing.
Like others have said you can get ice cream at many places throughout Disney. Beaches & Cream does a great milkshake at their to go counter, single scoop servings at Ample Hills, single scoop or a macaron sandwich at L'Artisans des Glaces, and the giant cookie sandwiches made with fresh cookies in every park are some of our favorites!