This is too raw for them. It is too soon and too painful.
I don't think your bf should be insisting the children meet you, or forcing them to accept you, this will almost certainly result in them digging their heels in even more.
Be compassionate about his wife, she sounds in a terrible way. Enjoy your life together and leave the family to recover and heal alone.
There is no reason for you to go to family events yet, no need to cause any kind of scene. Just bide your time and keep the door open.
In six months things may have improved, invite the children for lunch, spend time listening to them and getting to know them slowly. Take it at their speed not yours.
This is about them not you, always remember that their family has been shattered by this - you are a newcomer and not a welcome one when they are in the midst of picking up the pieces. But if you are patient and kind, then it will work out in the end. It takes years and years in some cases to get over such a long marriage, not months.
Stay out of it op. It is my best advice. Have fun times with your new relationships and let your bf sort out his family.