Do one session, spend the next few months practicing and honing your new skills whenever you go out riding, then maybe go back for some more.
You’ll learn so much in a day, it will be hard to process it all so quickly. You’ll need time to adapt and adjust everything so that it becomes habit rather than having to think about it, but when it has become habit, that’s when you know you’re ready for some more…
Oh, and my ex spent a day with Tony for her birthday last year, she’d only been on a mountain bike about 5 or 6 times in all prior to this, and though she had some natural ability she was an almost complete novice. By the end of her day, he had her getting both wheels in the air, cornering like a demon and ploughing through rock gardens without a care!