I translated the last bit as "He's a small friend". It's the translation that makes the most sense in the context because if the intended meaning for "petit ami" was "boyfriend" there would be a possessive adjective like "son" or "sa" meaning "his" or "her". Otherwise it's a bit like saying "He is a boyfriend" rather than saying "He's in a relationship".
All the grown-ups were kids at firstHe's a small friend.