Shawn says that he would like to establish a regular meeting schedule.

"To establish" (establish) means to create or to make something - to start something.

An organization might be established, for example, or created.

Shawn wants the group to establish, or create, a schedule for meeting regularly - for meeting every week or every month; that would be to "meet regularly."

Shawn says he wants a schedule of when the committee will convene.

"To convene" (convene) is a formal verb, a formal way of saying to meet, or to have people come together for a meeting.

You can say "We are going to convene a meeting," meaning we are going to have a meeting - we are going to meet together to talk.

Shawn says that when the group convenes, or meets the whole group, the committees will report back to the larger group about their progress.

"To report back" means to return to a larger group of people and give them information about what you have done since the last meeting.

So if you meet every month, you would report back to the committee about what you did in the past month.

Here, the committees are going to report back to the whole group to say what they've done.