My granddaughter is two years old now, so its high time that we started to teach her how to "pee" and "poo" on "potty" all by herself, trying to help her wean from depending on diapers. 

"Pee", "poo", and "potty" are all children usages for defecate, urinate, and toilet, respectively.  Okay, if you dont want to use kids words, and you dont know how to use that formal words like "urinate" and "defecate", then besides saying restroom or bathroom, you can also say you wanna "number one or number two", which is similar to the usages "小號" and "大號" in Taiwan. 

Interesting?  You bet!