No need to wait, I can tell you right now that you can indeed "add passengers" at online check-in and use different reservation codes to perform the check-in together. I am fairly confident, that you will also be able to select seats (unless the cabin is full and everyone else has already pre-selected their seats, which wouldn't be impossible, but certainly uncommon). I've used the "together check-in" option (like I said it reads "add passengers" on the left side of the page after you enter the OLCI process for the first passenger) and the system will try to assign you adjacent seats and it will even give you the same boarding group number (of course since you're both in business class it will already be just one boarding group, but last summer I checked my family in business class and at the same time my mother in economy and she had the same boarding group as the rest of us and boerded with us (which wouldn't have been the case if she cmhad checked in separately).
But: I would not even wait that long, I'd call the hotline right now and have them tell me my options. I haven't yet heard of a businesses class ticket not being able to get accommodated by calling them.