on the front i wouldn't be worried about one drop of fluid, especially if it works fine now, but if more leaks out you'll need to replace the seals.
As for the rear, you're looking at a rebleed, get yourself down to halfords or your lbs if it's open today and get some fluid.
Also, i wouldn't lube the pistons with teflon, don't know that it would do any harm but i use brake fluid so no probs with potential contamination or seal damage