He's a nice guy but not so considerate that he would think to have a surprise party for someone.
He's a very decent man but I don't think he's thoughtful enough to plan a surprise party for someone.
この場合、次のような言い方ができますよ。
ーHe's a nice guy but not so considerate that he would think to have a surprise party for someone.
「彼は優しいけど、誰かのためにサプライズパーティー開くほど気が利かない」
coinsiderate で「よく気が利く・察しの良い」
ーHe's a very decent man but I don't think he's thoughtful enough to plan a surprise party for someone.
「彼はとても優しいが、誰かのためにサプライズパーティーを開くほど気が利かない」
thoughtful で「気配りの行き届いた」
ご参考まで！
He's definitely a nice guy but I don't think he's the type of person who would organize a surprise party for someone.
ご質問ありがとうございます。
「彼はサ[プライズパーティー](https://eikaiwa.dmm.com/uknow/questions/38442/)を考えるほど気が利く人じゃない。」は英語で「He's definitely a nice guy but I don't think he's the type of person who would organize a surprise party for someone.」と言えます。
ご参考になれば幸いです。
カナダ 
アメリカ合衆国 
