“祝贺的人”可以翻译为 "those who offer congratulations" 或 "congratulators"（不过“congratulators”这个单词较为生僻，在日常使用中不如前一个表达常见）。
更常用且自然的表达方式是：
people who congratulate (someone)
congratulatory guests/visitors（如果指在特定场合，如婚礼、颁奖礼等，前来祝贺的宾客）
示例：The people who congratulated him on his success were numerous.（祝贺他成功的人很多。）
We received many congratulatory messages from friends and family.（我们从亲朋好友那里收到了很多祝贺。）