A good evaluation consists of two parts: attendee feedback and the internal debrief. Send a short digital survey with three to five questions the day after the event. Ask what they thought of the programme, what could be better and what they're taking away. Keep it short, otherwise nobody fills it in.
You do the internal evaluation as soon as possible after the event, preferably the same day or the day after. Discuss with the team: what worked well in the logistics? Which parts of the programme landed? What would you do differently next time? Write down the conclusions. After two weeks you only remember half: anything you don't write down now, you forget.