It is possible the upgrades to the Larian Vault could recognize the situation of multiple Paypal pledges from the same address, and let you resolve it as pledge and add-on. If not, then I think it will require a manual adjustment, if possible, after the work on the Vault is done.
From the kickstarter comments: 'The idea is indeed that you can manage your add-ons via the vault and that you can "upgrade" should you so want.'
