Happy would be sad and confused. He doesn't like to see his friends in trouble. He would fly around trying to gather information from different guild members. He would also stay by Lucy's side, trying to cheer her up. And all of her other friends in Fairy Tail would at least have some doubts about the decision. They know Lucy's character, and her sudden expulsion would make them question whether the guild made the right choice.
Natsu would probably be very confused and sad at first. He's used to having Lucy around, and her sudden departure would leave a big hole in his daily adventures. He might try to convince her to come back immediately.
Natsu would probably be really excited at first. He'd be all over the place, asking a million questions and making sure Lucy is okay. Happy would be right there with him, trying to help in his own little Exceed way. Erza would be very protective. She'd make sure Lucy follows all the proper precautions and would offer to train her gently so she doesn't lose her fighting edge during pregnancy. Gray might be a bit awkward at first but would soon warm up and offer his support, like helping with any heavy lifting around Lucy's place.
Lucy might be really surprised at first. But then she'd probably blush and say yes. After all, she and Natsu have a strong bond already.
Natsu would probably be very angry at first. He loves Fairy Tail like a family, so being kicked out would feel like a huge betrayal. He might go on a rampage, shouting and arguing with the guild members who made the decision.
The guild as a whole would likely mobilize. Erza would start formulating a strategic plan. She'd consider the strengths and weaknesses of Acnologia and figure out the best way to approach the situation. Gray would also be ready to fight, using his ice - make magic to support the rescue mission. They would all be united in their determination to get Lucy back safely.
One possible reason could be a misunderstanding. Maybe someone framed Lucy for something she didn't do, like stealing a powerful magic item from the guild. Another reason might be that she accidentally broke a very important and unbreakable guild rule without realizing it. For example, if there was a rule about not using a certain type of dark magic, and she unknowingly used it to save a friend.
Lucy might be heartbroken. After all, Team Natsu was like a family to her. She could initially go into a state of shock and disbelief. Maybe she would try to plead with the team to let her back in, explaining that whatever they thought she did was a misunderstanding.
He might be really angry at first. Natsu is a passionate character, and being kicked out unjustly would make him furious. He could storm off vowing to prove his worth and show the guild they made a mistake.
The guild would likely be ecstatic. Gray would probably make some snarky comment about Natsu finally growing up, but deep down he'd be happy for his friend. Erza would be all for it and might start planning the wedding immediately, giving orders to everyone in the guild to help out.
Lucy could be extremely excited. After all, finding Igneel is like stumbling upon a legend come to life. She would likely be in awe of his presence. She might immediately think about how this discovery could benefit her friends in the Fairy Tail guild. She could also be very respectful and try to approach Igneel in a friendly manner.