At heart, Man on Fire is really two stories; a bodyguard flick and a revenge flick. If you want things to play out in the same way, you'll have to run it over at least two sessions, IMO. Let the players get a long-term executive protection gig (with a precocious, adorable, kid) and run it long enough for them to get attached, IC or at least OOC, dealing with some day-to-day stuff or even a genuine attempt or two on their employer's lives.
Then, have a big fight scene where the kiddo gets snatched. You may have to fudge some numbers here, or maybe you can just stack the deck just right (so that things don't go the players' way, without them feeling like doormats OR getting totally wiped out and murdered in the face).
From here on out, the campaign becomes a little more standard Shadowrun fare again -- doing footwork, killing the guys who are between them and their MacGuffin (in this case the little girl), and having a good old time playing offense, not defense.
