I answer that the World Health Organization and Canadian Medical Association recommend breastfeeding until the child is at least two.

I like IxChel's answer. I usually say something like, "There's something called readiness and our son will let us know when he's ready to be completely weaned."

And you are totally right, weaning starts the minute they eat rice cereal and begin using their own sippy cup. Weaning is not a weekend process it takes months and every family has to do it the way they feel works for them.