If you have boys between 5 and 15 in your family, then you know about Minecraft, a popular creator game, based on a block structure, which makes them relatively easy to do in sand, especially fine-grained sand. Some of the main characters are Steve, Creepers, Endermen, Villagers.
Since the game’s characters are based on square blocks, these are very easy to carve in uniform sand. Just be sure you make a solid, wet pile of sand first, so it doesn’t collapse!
Minecraft Steve at left, and a Creeper.