This is a good idea. Please inform if your boss wants to keep it more technical or in general.
If on general subjects, my suggestion would be, tackle those issues or subjects of your day to day coordination e.g. -
1. How to follow the timelines,
2. Discuss ideas of best team skills,
3. Interpersonal communication,
4. Even ideas how to keep our company culture up to the mark or raise it to the optimum,
5. Challenges being faced / that will be faced in future by IT industry and how to overcome it
6. Customer service related
7. Even Work life balance etc.
8. Everyone to brief his tasks on hand and the support required from others, if any
Kindly note, the discussions should happen as a brainstorming session without pin-pointing on any person / personnel in the organization. You may target certain behaviors /incidents but not the persons. The motto should be a fair exchange of ideas to arrive at a win-win situation.
Hope this helps.
With best regards,