Reality, I wouldn't have thought the social worker MOC would be limited to the army, but rather you could choose which element you wanted. I'm applying for JAG and it doesn't have any restrictions; I'll probably choose Navy (If I get a call that is)
Have you any idea where you might be posted as a social worker. That sounds like an interesting profession to be doing in the CF, I wasn't aware there were social workers in the CF - is it a new trade?