もしあなたとの取引が成功したらカードを数枚同封するのでアメリカ人の友人に渡せるのなら渡して欲しいです。無理にとは言いませんが。
If I can succeed in a deal with you, I would like you to give some of them to your friend in the US as I will enclose some cards. This means that I am not forcing you to do this.