Getting iPhone 12 with store credit/trade-in

Hi there,

I currently have an iPhone XR and have been waiting for the new iPhone 13 to come out so that the iPhone 12 and 12 pro prices drop (which is the replacement phone I want). I was planning to use the trade-in value of my XR towards the new phone but I also have other devices, an iPhone 8 and a MacBook Air (2015), both of which are in perfect condition, that I was hoping to get a store credit from to also use towards the phone. My question is: can I apply for the store credits from those two devices now and then wait to use the credit when the prices for the iPhone 12 and 12 pro drop, or do I have to bring all the devices in at one time to do the transaction?

Please let me know,

Pippa Bridges