I think one issue here is do you want to be a good neighbor or a good foodie? If this a group of people that you like and would like to be part of I would say go with the group recommendations and make a casserole. And make a really good one that your neighbors will like. It's a social group not a foodie competition. If your host asks for a casserole they probably have the other courses taken care of - don't step on their toes.
Edited to say: I hate it when people arrive at a dinner I have all planned out with something that does not fit in. "They just HAD to bring something.!" Do others here feel that way?