Not sure if you want to dive straight in, why not just dip your toe to start with. Here are some block building apps that you could use to start your students off.
Minecraft — Pocket Edition is a Universal App! Minecraft is about placing blocks to build things and going on adventures! Pocket Edition includes randomly generated worlds, multiplayer over a local Wi-Fi network, and Survival and Creative modes. You can craft and create with your friends anywhere
Minebuilder is a Block World game which lets you create your own adventure. Craft your tools during the day, fend off the monsters at night and when dawn comes again build your own world, alone or with your friends! Minebuilder contains a large number of blocks and tools with which you can craft your world.
Eden: $0.99 AU
Explore a world of limitless possibility. Build your own personal Eden. Unleash your creative and adventurous spirit. There's lots of places to explore. Lots of creative possibility, and you can download all kinds of things. Beautiful endless worlds to explore, build, and destroy. All kinds of blocks, ice, water, lava, glass!
You are marooned on the shores of an infinite blocky world. Explore, mine resources, craft tools and weapons, hunt, make traps and grow plants. Build a shelter to survive nights and share your worlds online. Ride horses or camels and herd cattle. Build complex electric devices.
Lunacraft welcomes you to a future where you can explore and colonize a new alien moon every time you play. Meet strange new aliens, some dangerous, some helpful! Establish a base of your own design with dozens of materials, harvest alien light trees, and decipher clues left by astronauts to create exotic technology!
Imagine, create and build amazing worlds. With dozens of building blocks at your disposal, let your creations take formatio and your imagination run wild. Introducing new elements for enhanced gameplay; interactive characters, animals to special construction blocks. Free Play mode - Random or Flat world.
Create your world, explore universes and random worlds created by others. Build whatever you can dream of with many users online. Play with your friends or random people online! Multiplayer and Single Player "Creative mode". Ability to create password-protected maps exclusively for friends
Adventure With Companions is a game that lets you place blocks with others to build cool buildings and mine caves in an online world. The changes you make and your location will all be saved. Meet new friends, build whatever you want out of blocks and work together using chat.
If you can imagine it you can build it with the six Toca Builders! Join your new builder friends on an island far away and create a whole new world with blocks. Jump, walk, roll and rotate the builders to use their unique skills, and they will help to build whatever you can imagine! Toca Builders makes it fun to build.
Create, Move, Build and Dream in 3D Space! No limits to your building fun! Even Rotate Blocks in Space Hands Free. It's here! Block Building on your iDevice Screen! Build anything you can imagine and bring your Dreams to Life right on your iDevices for one price!