You will have a couple of options in this scenario:
1. Keep your current Jeppesen subscription. You will be able to link your Jeppesen account inside the ForeFlight Mobile app using your Jeppesen credentials. Please note that this option will use one Jeppesen license (token) per device.
2. Contact Jeppesen to cancel your Jeppesen subscription and repurchase through the ForeFlight website. With this option, you will have the ForeFlight individual license model that will allow you to use Jeppesen charts on all of your allotted devices (one iPad, plus one backup iPad, and one iPhone).