You shouldn't do things to others that you wouldn't want happen to you.
「自分がされたくないことは人にしちゃダメだよ」
- You shouldn't do things to others that you wouldn't want happen to you.
アメリカでよく言うことわざ（？）は：
- Treat others how you want to be treated.
他：
Would you want them to do that to you?
- 友達にそうされてほしい？
Don't do things to people that you wouldn't want them to do to you.
You shouldn't do things to people that you wouldn't like yourself.
この場合、次のように言うと良いでしょう。
ーDon't do things to people that you wouldn't want them to do to you.
「自分にされたくないことは人にしたらいけないよ」
ーYou shouldn't do things to people that you wouldn't like yourself.
「自分が嫌なことは人にもしちゃダメだよ」
ご参考まで！
Don't do to others what you don't want done to you.
英語では Don't do to others what you don't want done to you. と言うのが一般的です。これは「自分がしてもらいたくないことを他人にしてはいけない」という意味になります。
子どもに伝えるときは、もっとシンプルに
Treat others the way you want to be treated.
（自分が扱われたいように、他人を扱いなさい。）
アメリカ合衆国 
カナダ 
