Never had specific experience with SK, but in general with other airlines most special requests, ie special meals, or kids, will kill any chance of an op-up.
Regarding upgrade w/special meals on SK, this is no longer a problem and has been ok for over a year. The only thing to remember is if OT upgrades you in advance, you have to call to SAS and request the special meal again.
If it is less than 24 hours before the flight and you recive the upgrade, they will move your meal from Y to C. Then again making in obvious who´s got the upgrade
