I don't see why the sunny wouldn't float if it is given a DF. The sunny is a boat, boats float because of physics and buoyancy and whatnot. A DF would not have an effect on that. More so, people with DF sink because they get paralized and can't swim, not because of physics violating magic.
As for who will get the fruit.... No clue, there really are a lot of strong people there. Burges would be a very realistic candidate but I don't think luffy will allow for that to happen. What if garp suddenly appears and takes the fruit for himself? It is also a strong possibility that luffy will get it and simply keep it as a memento if no one in his crew wants it.