I am the informal president of the local brew club here.
First, decide among your members what you all want to get out of the club. We started out as a group of people that got together and made beer, then became sort of a social club. Everyone would bring beer and we'd just party. A few months ago we had a club discussion and decided to be more educational. Open it up to the members.
It is a little difficult to start. Like you I need fresh ideas for the club to do every month. Furthermore I need to find volunteers to participate.
Have something at every meeting
It does not matter how small they are (as long as most of them are engaging).
Style of the month
We feature a beer style every month. Encourage members to brew their own or bring commercial examples. That opens everyone up discuss the style. Last fall we had 7 or 8 Oktoberfests and did a very good tasting panel. It helps homebrewers to announce the style at least two months in advance.
Have something to talk about. This month we discuss aeration techniques. We had a water chemistry lesson, a brew-in-a-bag demo, and a how-to on making yeast starters in a ziploc bag. In the beginning it may be only things you are interested in, but other members will pick it up.
Do big things every once in a while
Every few months have a bigger club event. Brew-ins are usually successful - everyone brings their equipment somewhere and we make beer.
Our club got a wine barrel from a local winery and we had a club filling day where we put 55 gallons of RIS.
My previous had a yearly brewery tour by bus.
I think once you get going the ideas will come on their own.