Lab-meetings: How to establish a good setting?
This is a fine strategy. See how it goes, and discuss afterwards whether it was helpful or not. You should not allow your meeting to run any longer than ninety minutes though on any account. Most people will not be able to concentrate for that long. Also consider inserting a break if it is going to exceed 60 minutes.

Some other thoughts: Instead of having every contribute every month, consider having only one or two presentations each week. You will probably find that some people assume that 45 slides can be presented in eight minutes and you have to cut them short or cancel the later presenters.

Keep the first session very positive and upbeat, don't be afraid to step in as the moderator if anything is going wrong. If the students make a hash of things, so be it. The first meeting will set the tone for the rest, so if someone spends thirty minutes dissecting the student's presentation, no one will want to come to your next meeting.

In that respect consider giving a short presentation on your own work/goals yourself, so that everyone has a good example presentation to emulate.

I would say it is not really fair to insist that everyone prepares some food for the group to consume. Your team are scientists, not caterers. ;) My advisor used to contract external caterers for our team meetings but I think he was a bit over the top there.