Hi Maria, Brendon here.
You could definitely say, "ride on a swing". In this context, the word "swing" is a noun - that's the name of the object you're riding on. In the US, you ride on the swings (swings being the name, ride being the verb). Grammatically, it's correct to inquire if one can "swing on swings", because "swing" is an action verb and "swings" is the name of the object in which you're swinging on, which is inherently a noun.
Surefire method is to say, "can I ride on the swings".