Hi Julii_
Welcome to the Apple (user-to-user) Community.
Re: can I trade-in both mine and his old iPhone?
To be quite sure, you would need to check with someone working at Apple.
No-one here in the Community can speak for, or make a promise for Apple.
We are all Apple users, like yourself.
We'd like to help, however.
When making an online iPhone purchase, there are opportunities to "chat with a specialist" and a specialist would likely be the best person to ask.
Else: On Apple's "Trade-in" webpage
Trade in with Apple Trade In - Apple
In the Frequently asked questions at the bottom:
says:
Q "Can I trade in more than one device at a time?
A You can trade in as many devices as you like,
but we accept only one device per transaction".
Q "Do I have to provide proof of purchase for the device I’m trading in?
A No, proof of purchase is not required to trade in a device with Apple TradeIn".
_______________________________________________
If needed:
Other support options:
Apple Store Customer Service at 1‑800‑MY‑APPLE
Shopping help: Help - Apple
or
Payment & Security - Shopping Help - Apple
or
Apple phone numbers around the world
:Contact Apple for support and service - Apple Support
All the best :-)
