^I'm in the same boat, basically.
It's my understanding that a lot of people set up LLCs not only to help protect against lawsuits, but also because of the way US tax laws are set up. If you're not in the US, YMMV. But oftentimes, people are taxed less as an LLC than they are as individuals. That depends on your state and what kind of LLC you have, though.
If you want to set up one, talk to an attorney. They set these up all the time and they can walk you through it.
As for suing because the sitter got bad advice? Sure, they can try, but I doubt any judge would take the case. You're an entertainer, not a doctor, and there's a huge difference. Mainly the fortune teller license bit is to prevent people from things like the 'setting lights' scam and things of that nature, as well as to make sure the reader's paying taxes. But trying to sue you because they got a bad reading smells to me like it'd be up there with suing your bartender because they gave you bad advice. It wouldn't fly in court IMO.