My son has a child's account on my Windows 10 x64 machine. I've been letting him install pretty much anything he wants from the Windows store, since with him running under a child's account I think this is pretty safe.
However, he wants to install Steam so he can run other games. My understanding is that Steam is basically a Linux virtual machine running on your machine. I would assume this would be running as a desktop app and I would probably have to install Steam as an administrator. Would Steam be usable from a child's (non-administrator) account on my Windows 10 laptop.
I wouldn't really worry about running applications on, say, Oracle Virtual Box on my PC; although I know that it is possible to attack the host OS. How curated is Steam's store and is it possible to install Steam games from outside Steam's store?