I was very active in a local guild that ended up dis-banding because the founders had mostly moved on to other phases in their lives and we did not get enough new members who were able to fill the positions. A guild needs several people willing to serve on a board to function as a guild. Most guilds have a mission statement that includes providing education and doing some pubic out-reach. If you do not have 3 or 4 really strong calligraphers who are willing to teach, you would probably have better luck starting a club. You might consider calling it Penmanship, Cursive, Lettering, AND Calligraphy Club. Limiting yourself to just calligraphy can be misleading to those people who want to explore some of the more contemporary styles.
The two main things you need are a place to meet and a form of publicity. Libraries often have meeting rooms and are welcoming to groups. Art supply stores can be very welcoming if they have a space for class rooms and if they see an opportunity to sell art supplies. Same with craft stores such as Hobby Lobby and Michael's. Some of them are very welcoming and provide good publicity. Sometimes malls have space in the food court that can be used for meetings during off hours.
A club that welcomes both parents and children is always a good idea. If you really want to pursue this, I would be happy to offer more suggestions as well as a long list of topics that you can offer. Most groups like to meet for 2-3 hours and have half the time spent on learning something and the other half of the time looking at work and helping each other with projects.
Our guild met during the school year. Attendance was always down during the summer so we did not meet then. We sometimes skipped the Dec meeting as that is a busy time of year. We focused half the meetings on actual lettering styles and the other half would offer projects where people learned ways to put their lettering to use. Cards, etc.
Let me know if you want more suggestions.
Social media probably makes it easier to publicize gatherings.
Since many schools are dropping cursive, a Cursive Club might attract a nice group of people.