You really think they would give an empty seat to my son over upgrading someone else? Even when my ticket is an award ticket?
If Economy is not overbooked they will not upgrade anybody. If there is a extra business seat empty, they will place you next to it. But they try to do the same if you fly economy and the flight is not full.
I also did it already in Swiss business, flight was full so we had to hold him the entire flight. In business, not so bad.
I do understand people getting upset in First. People pay close to 10000 Dollars to get a good nights sleep and have a small baby next to them? I think its not right for an airline to let little kids in to First. But as long as they let, its not your problem. I personally would never take my baby into first. Since I know people will be pissed, I would be way to nervous the entire flight, making sure he stays quite.
A guy once told me, if your baby cries, walk back to Economy and quite him down over there :-)