I don’t think any one extends the timeframe to complete your trade in for the holidays…Google just happens to give 30 days (the danger in what you mentioned is that they will reevaluate the value and it’s very possible that the value may be lower once that occurs). Some providers also give 30 days to turn in your trade in so you may want to check into that as an option. Keep in mind that it’s not that you can’t send your device in after 14 days but like Google, your trade in estimate is for that specific time period and would be reevaluated if received afterwards. You can always contact Apple’s Sales Team directly to discuss things to get clarity and be sure that even if returned after the 14 days your trade in can be applied to your purchase as intended.
Depending on what method you are using (Apple Trade in credit, Carrier trade in device payment plan, Apple trade in using Apple financing) it may affect the way things occur. Example…if you are doing a carrier financed device payment plan and receiving the Apple Instant Credit you may have the trade in amount charged to what ever payment method used to pay the taxes since the carrier has already received that instant credit amount. When your trade in arrives to Apple and is still in the condition reported you will then receive a refund back to the payment card for the amount that was charged when the trade in wasn’t received. But again, this is all what will be clarified when you speak to the Apple Sales Team Customer Service (make sure you are speaking with the correct customer service so you receive accurate information).
If none of that is acceptable to you and you can’t just wait to closer to Christmas to buy the trade in and avoid issues and your frustration pushes you to going to Google that’s just a choice you would have to make. But since you said this is a Christmas gift you might want to make sure buying a Google phone is what the person you are gifting would want. Won’t do you any good if they only want an iPhone. Or…you could go through the carrier if they give 30 days to send the trade in. You have options. Just up to you to choose the best fit. Oh..you could also choose a creative way to let the person you are gifting know they will be getting a phone (only thing limiting you is your imagination or inspiration you can find by searching online for ideas). If Apple is the place you would prefer to do the purchase from you can then place the order closer in the window that won’t affect your ability to send the trade in back in time…or if there is an Apple Store near you take the receiver to Apple on the day after Christmas to pick up their new gift. One year I gift wrapped a custom iPhone case for my son with a card letting him know this was for what was on it’s way (this was not a Christmas situation but a birthday one where the phone wasn’t arriving until after his birthday).