Tie (hand off) sub-domain shopping cart to higher level domain?

We have a normal eCommerce site set up on our domain (cellperspectives.com) with WooCommerce.

On a fresh WP install on a sub-domain (specials.cellperspectives.com), we have some very focused/targeted landing pages that are about to get built (no site nav, just call-to-action).

The owner wants the sales funnel to be handed off to the main site at some point in the process.
He has a wish on where in the funnel it’d be handed off, but fortunately he’s open to whatever is needed to make it work best.

Is there a way to have them populate their cart on the subdomain, but then hand the check-out portion of the process to the main domain?