I think what you are trying to accomplish is very nice.
As for instant coffee, it's not a perfect analogy, but instant coffee seems rather like ice tea powder. I suppose it's coffee, but it's really not the same as the real deal. Starbucks brand is, I think, better than most others, but still not the same. If you don't mind buying some I'd buy the packets from Starbucks since you can buy a limited number of them, alternatively, you can always say you only have tea, but there is a Starbucks around the corner.