A lot of people into the hippie side of psychedelic culture don't like pharmaceuticals because they're unnatural or whatever, but in practice, there's a chance that your psychedelics are going to trigger hours and hours of rolling panic attacks that feel like you're dying, to the point where you may convince yourself that you've certainly died, or perhaps that you've never been alive.
You're considering ingesting some very weird chemicals. Have Xanax on hand just in case, so you can essentially put yourself down. If you have to take it, you'll still be tripping but you simply won't care, you'll not remember much, and you'll have turned one of the possible worst PTSD-triggering experiences of your life into a "meh, that sucked" experience.
That said, you might have a great trip that opens your mind and changes your perspective on life. I'd say it's 100% worth it if you're in the right set/setting, but not worth the risk of having a terrible time without an benzodiazepine escape hatch, because things can get seriously uncomfortably weird.