An ex bf from highschool moved to the city not too far from where I currently live. He’s been here for two years. I want to meet up with him and catch

Up platonically. I genuinely want to know how his life is going. I have no romantic interest in him… However I am currently with a guy and I’m debating whether I should tell my guy the truth about wanting to meet up with him for lunch or should I just go to lunch and not say with who??