I'd recommend against sand , if you must use some , I'd recommended high grade PLAYSAND - it comes from rivers banks and is eroded so has very small surfaces from being tumbled about in the river.
Many Australians who keep dragons swear by PlaySand even for the youngest hatchlings.
I think personally you dragon will enjoy lose eucy bark and twigs and dried eucy leaves much more . No bark or twigs small enough be ingested though so if there are fine particles in the bag , screen it and only allow chunks too big to be swallowed.
I'm lucky - as I have an endless supply of eucy leaves , bark and twigs , that shed from my mature bluegum ( in my front yard ) so all I need do when I need some is step out my front door and down 4 steps and it's all over the lawn ( especially after a period of heavy rain or storms ).