In short if you invite people - you pay for them! People who are not invited should not invite themselves unless they are willing to pay. If he wants to pay for his own ticket that might be okay and since you invited her you should be paying for her anyhow.. he shouldnt be paying for her if you invited her.
Your ex pays for himself and his/your daughter. Your older daughter's boyfriend pays for his girlfriend and himself. You take care of your own ticket.
Dutch treat split 3 ways.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.