Welcome to the wedding planning world! There are lots and lots of posts very similar to this of just letting it all out. You would be surprised by just how many brides get this same kind of flack.
Just remember, this is YOUR wedding. They had plenty of time to give input and chose not to. It seems that no matter when or what you do, there will be something they will complain about. They did not offer to help pay when you were looking to book, but now they want to give you money change it? That is just ethically wrong. Had they wanted to help pay from the get-go, yes, their input would truly matter. If they REALLY want to be there, they will. If they do not go, they will secretly regret it.
Do what is going to make you and your fiance happy. Changing wedding plans may not make up too unhappy, but will they find something else to gripe about? My fiance has told me he is glad I handle all the wedding stuff because we have had so many people wanting us to change things. I simply smile and say "because that is not what we want" and go about my business. My poor fiance would feel guilty and try to suite everyone else instead of us. Good luck and do what you feel is best for your situation!