I have the lake house too and when drinking that was all I did out there, then waking up feeling like crap and just wanting to be lazy, yet also bored because you're out at the lake, stuck. Sober you take on projects, make it nicer, work on things, cook up good food, boat around without fear of getting pulled over drunk by the police boat (same DUI charge as a car here). I already have a list of projects to do.
As for the other things on your list with enough sober time under your belt you'll also have fun regardless of the event. I've been sober up to 2 years before, all the booze thoughts you're having right now do go away and you just live your life normally.
I've even been to the cottage sober, it was fine.