@Evgeniy's answer is the best solution for something search engines are not designed to do, which is trawl dynamic pages.
You should clarify with your stakeholder whether the content actually needs to be loaded dynamically, or does it just need to be shown/hidden dynamically. If it's the latter, then you can include all the content in the original markup, then show/hide with css display:none, or jQuery toggle (same thing). If your content is bandwidth heavy like photos or videos, this may be a no go, but if it's just text, then text is cheap. Preloading and show/hide will let search engines trawl content and save you a heap of trouble.