About Jenna, again, it's her board. So, she can pop in whevere she likes. However, people don't know she's popping in and, as mentioned, there are few people in the chat room (at least, when I have visited).
So, my suggestion is to have a structured, 30-minute chat. Have her open it by giving some background and anecdotes. Then let her answer the obvious questions ("How'd you get the Celine Dion gig," "How do you curb the anxieties before getting published?" and so on. Again structured. It makes her look better. It makes you as the moderator look better. And give people more access to her. Finally, it helps others whom you may schedule to know what they'll do. You and the speakers can also set the ground rules early on with planning.
On other forms of chat, there are CGI based as well as flash based chats. The CGI based chats are slower, but are easier to use and perform the same function. The flash chats require a technology to use (Flash), but, ultimately, are easier than Java or IRC.
Finally, I'm absolutely willing to help wherever. This is a fantastic forum. I relish the interaction and I've gained a great deal in my short time here.
Thanks.