Don't play around while brushing your teeth! Do one thing at a time.
Don't drink tea and walk at the same time! It's dangerous!
Don't go down the slide while holding a toy in your hand!
ご質問ありがとうございます。
① "Don't play around while brushing your teeth!"＝「歯磨きしがら遊ばないで！」
"Do one thing at a time."＝「一つずつやって。」
② "Don't drink tea and walk at the same time!"＝「お茶を飲むのと歩くのを同時にしないで！」
"It's dangerous!"＝「それは危ない！」
③ "Don't go down the slide while holding a toy in your hand!"＝「滑り台をしながらおもちゃを手に持たないで！」
ご参考に。
アメリカ合衆国 
