Have you asked the attendees what they'd like to do? (may sound rude but doesn't mean to be!) May lead to some interesting points and feedback, or a case of "we like it but I don't read up on Web stuff much" that's interesting to know too.

In the few CoPs I've helped organise over time:

• Running a low-effort retro to see what's working and not working for folks can help - we did one which highlighted that a load of people wanted to dig into a specific subject, but no one had voiced that 😅
• Rotating who's organising (preferably volunteering over voluntelling) can add a bit more variety - even if it's just the CoP leads/most senior folks to start with? Then can be rotated around with other folks too
• Running a lean coffee was a good way to get to chat about things in a less pressured way than folks feeling they had to present something big for the session
• Starting each session with a different engineer (who's been voluntold ahead of time) who does ~5-10 mins overview of their team, what they own and some of the stuff they've done gives a bit of an insight into what everyone does - depends on how much involvement folks get cross-team, but at a previous company this was super useful as it was a bit more silo'd