I think I am a bit odd, but whenever I donate, I opt-out of gift aid, so that I don't have to remember the values for the tax return (hate filling in forms). It's often difficult to opt-out of it too. Sometimes you have to select that the donation is from someone else, or you have to select that you aren't from the UK. It's rarely a yes/no question. Like I say, I'm odd. :)

By the way, good luck. I think KS would have given the project more momentum, but JustGiving is fine too.