(Bear in mind the overall "transaction fee" percentages for the entire drive will be lower than what's on that page, since any donations that don't use the widget will lower the average.)
Edit: For anybody playing along, those calculated donation+fees were incorrect for about 3 minutes, before I realized that I wasn't doing my algebra right. That is, if you want to end up with $x , and they tell you fee= (sum *.029) + .3 , you can't set x=sum, solve for fee, and just add it. You have to set sum - (sum*.29 + 3) = x, then solve for sum.
This is why I'm glad I don't have to do this alone.