What's the word for a gifted service (or intangible good)?

Solution 1:

Yes. Gesture is the word.

Gesture

any action, courtesy, communication, etc., intended for effect or as a formality; considered expression; demonstration

[Dictionary.com]

And that's one awesome gesture, to say the least! I trust you were all taken by surprise by your company's gesture! Why don'y you just say that?

Thank you so much for the sweet surprise. We thoroughly enjoyed our time and this gesture will forever be etched in our memories !

Solution 2:

[Christmas] treat might convey what you're looking for.

treat

: an event or item that is out of the ordinary and gives great pleasure. ODO

: a) an occurrence in which you pay for someone's food, drink, or entertainment; b) something pleasant or amusing that is unusual or unexpected M-W

: a) entertainment, food, drink, etc., given by way of compliment or as an expression of friendly regard; b) anything that affords particular pleasure or enjoyment. Random House