Your answer makes sense and is in line with what we were thinking.
However, just in case an emergency were to come up and we needed to travel (with the baby) before July 2015 then what would my options be? I am a Kenyan PP holder and my wife is a Pakistani PP holder. In this case, am I correct in thinking that I would have to first get my son a Kenyan PP and then apply a PBS dependent for him as well? If so, does this cause any complications (or delay) with him getting a British PP once I am on ILR?
Also, I finish 5 years on Tier 2 in July 2015 (i.e. been on tier 2 since July/Aug 2010) whilst my wife who is on PBS Dependent under my Tier 2 has been on this status since October 2010 (i.e. 2-3 months later). Will she automatically get ILR too? both our visas expire on the same date in July 2015.