Digital Socratic Seminar
Consider using a Google Doc and having students silently type and share their ideas. This eliminates the "everyone is watching me" feeling and pressure that can sometimes be experienced in Socratic Seminars. This can be very busy and sometimes overwhelming when a class of 20+ students is all accessing one document, but it can also be very excited for 20+ students to be sharing their ideas and questions with one another too!
Last but not least, create a blog and have students respond to one another on that blog, or start their own threads of discussion. The edublogs platform is a safe place to do this where you can moderate content and approve student posts and comments, make it private to just those students invited, and even group students and monitor progress and activity. This would be very similar to what students might be expected to do in an online class in the future, so try it out!