I get the impression that there are far more requests to be "closer in" and highest floor possible (the views at OKW are lovely from the higher floors, and are often a lot of vegetation on the lower floors). It seems like your chances of getting what you want would be pretty good even upon arrival. I've stayed at OKW 3 times now, never requested a floor and have always gotten ground floor, which, with a stroller, I really appreciated. Good luck!