Good evening Paul and welcome back!
Thank you for reaching out to us.
I would love to help you with this topic.
There are a couple of ways to go about your client’s main requirement: to make sure the attendee pays the conference fee.
One of the best approach in my opinion, would be to use a plugin such as: http://www.itthinx.com/plugins/groups-woocommerce/
This way you could make the conference fee a distinct WordPress product that would unlock access to the other products which would otherwise be impossible to purchase.
Keep in mind it is also possible to redirect customers to a product page through customization.
You could even combine this with one of the following plugins: https://docs.woothemes.com/document/chained-products-vs-product-bundles-vs-force-sells-vs-grouped-products/
That being said, there are no direct built-in way to do this.
If this is outside of your comfort zone, you might consider hiring one of our recommended customizers to do the customization for you.
Best regards,
Geoff B.