Well, one could argue that in the first film that Michael did A.) like to scare and toy with his victims and B.) did have his own warped sense of humor (with Bob's ghost costume and all as opposed to just hacking and slashing. He was playing cat-and-mouse a number of times as opposed to just killing. And it's not as if the writer is saying that going after children is all Michael's about--it's one isolated incident overall in the arc that the author is doing. The other comics elaborate more on why Michael is doing stuff like this.
Here's what the author said:
"For me, remaining true to the source is the actual freedom. And by the source, I specifically mean the original film. There’s so much scope for decent material lying latent within that original film which was never utilized in the sequels. A lot of the mysterious and creepy elements of The Shape were forgotten for the films afterwards – you know, the bizarre and dark sense of humor (e.g. wearing a sheet over the head), the scaring of the characters just as much as the killing (look how The Shape stalks Laurie Strode and lets her see him to creep her out). Also, the fact that in the first film, The Shape is a complete absence of personality—a void—leaves the character much more open to interpretation and less restricted than in the sequels, where he became pretty much a family killer and nothing more.
The way I approach it, is to define The Shape by his actions, and by how he is perceived by others—it goes back to the blank slate of the original. All we know is that he’s a voyeur as much as a killer, a hunter that slowly stalks his prey, a prankster of sorts who really messes with the heads of his victims, occasionally sexual and perverse (see the difference between how he watches and pursues women to men) and a sadistic, evil bastard with no redeeming human qualities whatsoever."