These can be awesome fun to build and to play in. Just a safety note...
If you build snow&ice structures, keep in mind that some can be dangerous for young kids who later come across this very compelling structure.
Especially igloo/cave/house, or other structure that can otherwise collapse atop small ones.
Even if structurally sound when built, it can change rapidly over time, due to melting, snowfall, and play.
If you can't check it frequently, to make sure that it's not in a state that can collapse and result in tragedy in a matter of minutes, then you probably want to disassemble it (and spread it out).