Although the choice is yours, I would advise for it to be unactivated. That way the prize is something they can keep as an FTF reward, rather than a coin like any other that they have to move along.
If activated, it would be marked as collectable so they would have the choice of keeping it or moving it along.
I was leaning towards unactivated so they can choose to keep it as a memento of the FTF if they wanted, or they could send it packing and watch it go along with them. Or they could sell the coin or use it in a poker game.
It seems like unactivated it would be more of a prize.
I was mostly wondering what most people do for FTF coins.
I have gotten an couple FTF trackables and they have always been unactivated. If you do activate it, then it would need to be transfered to the lucky cacher.