The good thing is that if you start with bubba when they're newborn, their weight will increase gradually and you will get stronger. I don't think I would have done too well carrying a 10kg toddler all of a sudden but I have worked myself up from 3.9kg and I'm fine.
By the way, I know exactly what you mean. I have the nickname "GG" or "Google Geek" for a reason

Saša