Unless you have a cellular or mobile data hotspot and exceptional bandwidth and a GREAT computer, and some luck, DO NOT use Smartmusic for S&E anymore.
It's 100% mobile, and you can't download the accompaniments for offline use the way you used to. This means you're totally at the mercy of the Internet gods. And since everyone's S&E is in the same two-three week period, their servers will be .. heavily used.
You're better off getting a CD-quality recording of the accompaniments somehow by paying a pianist and having your kids play along with that.