The last person to play with the toys has to clean up.
Whoever plays with the toys last should put everything away.
この場合、次のような言い方ができます。
ーThe last person to play with the toys has to clean up.
「おもちゃで最後に遊んだ人が片付けて」
the last person to play with ... で「最後に…で遊んだ人」と言えます。
ーWhoever plays with the toys last should put everything away.
「おもちゃで最後に遊んだ人は片付けて」
whoever plays with ... last で「…で最後に遊んだ人」とも言えます。
「おもちゃで遊んだ人みんな」と言いたい場合は、次のように言えますよ。
ーEveryone who was playing with the toys should help clean up.
「おもちゃで遊んだ人はみんな片付けるのを手伝って」
everyone who was playing with ... で「…で遊んだ人みんな」
ご参考まで！
カナダ 
