Is it the boy dad who finally came to save them in the youth Shanshan Island movie?

No. According to Douban.com, it was the rescue team, not the boy's father, who made the last rescue on Youth Coral Island. Coral Island of Youth is a drama film directed by Randall Cleather and starring Ji Bo Su and Christopher Atkins, which was released in the United States on June 1980. The film tells the story of Amy and Richard who survived a shipwreck and lived on a desert island.