We found a recipe for pickled green tomatoes we're trying out. Let you know how it goes.
If you have 13 kilos you should probably freeze some of it. I would probably roast them first. That will make them a bit less sour and they will contain less water thus it takes less space in the freezer. Oh and discard the super tiny ones, they will just make the rest of them taste bed.
Oh and you can use them in any soup or sauce and you won't be able to tell they were frozen.