The idea would probably work well with young learners: if they have something to tell you, like they won't be coming to class, or have forgotten their homework, it's more fun than just an e-mail.
Problems with Moviemaker
There are a couple of minor issues with Moviemaker, one being that it starts to play automatically, so if you embed it on a blog as I've done here, you get that disco beat whether you like it or not (you do have an option to have no music — but that's not going to interest a kid!).
Nor can you edit your movie once you've finished, so you can't then remove the sound track (or correct any other errors). It's also a drawback that you can't record audio.
You'll also find that some of the characters you get (scantily-clad ladies, for example) and some of the possible settings for your movie (like, bubble baths!) are perhaps not entirely suitable for young learners.
Lots of fun, however!