Can I trade my iPad Air 2 for a later iPad model?

You can verify eligibility for trade-in and obtain an estimate of the potential trade-in value here:

Apple Trade In - Apple

You should be able to trade-in at a physical Apple Store - many choosing this option by preference as the device can be checked, the trade-in value finalised and the process completed while in-store. Be aware that Apple’s in-store trade-in values may differ from the on-line estimate.

Before parting with your iPad, whether trading-in or selling privately, ensure that the device is properly prepared:

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

you can trade a wide range of things in also some non apple made items and you can spend the trade in price for whatever you see fit, read more about trade in here

Apple Trade In - Apple