If it were mine I'd take something along the lines of the second option, except before lautering the mash (but after mashing) I'd rob the sparge water of a little over a gallon, boil it and add the boiling water to the mash. This will give you more equal runnings without the thinner mash. It will also bump your mash temp up a bit to offset some of the cooling that occurs during lautering and while mashing in a cooler. This is also why many batch spargers use water hotter than 170 to batch sparge. I've also found beers that don't get the extra heat at the end to be a bit thinner and/or attenuate more. YMMV, and I'm assuming you're batch sparging in a cooler still. There is also a setting on beer smith that will calculate out the water additions using this method, but I'm on the road now and don't have it with me. Dennybrew.com also has this formula.