If you bring them in to bond them at this time of year as long as the room isn’t heated then it won’t be a problem to return them to outside again. Unless you are going to camp outside too how else can you be close by overnight at the start of bonding ? IME it adds unnecessary stress for the Rabbits to bond them by separating them and putting them back together again time after time. I am not saying that doing that can never work, just that IME it has never been necessary.
I have bonded Rabbits using my bathroom as the bonding area. I don’t know your housing situation, but is there no indoor area anywhere that’s away from your bonded pair? Bathroom, kitchen, hallway ?If you neutralise the area you used before to try to bond the trio, using a dilute white vinegar solution and moving around any furniture etc to make it smell and look different the buck could be tricked into not recognising the area.