本当にありがとうございます！

Hello Isabella, Here is my contribution : In the first sentence the particle に is used because 日本全国 is a place and ある is used for inanimate things. これは「おもちゃ病気」と言って日本全国にあり、コミュニテイー・センターや図書館で活動している。 The phrase is as "there are in Japan in the community centers and libraries of the actions called "sick toys ". 子供たちを笑顔にすることだそうだ。 Here に uses to indicate a change occurred, the cause was generated by someone or something (transitive). In this second sentence, it could be by the actions of the centers and libraries. "This action seems to delight children. " There is also a second use of にする ! It serves to say that we have decided something when we have an option or a choice in front of us. そして、子供達は、物を大切にしてかんしゃすることを学ぶ。 This sick toy teaches children to cherish things and take care of them ! I hope it helped you to better understand the 2 notions of grammar and the meaning of the text ! Sunhi