JWs can make a drama over anything. I would suggest to your wife that as you are not included in the invite it may offend her brother if you contributed to the wedding by paying for your wife's travel and accommodation. Perhaps it would be better for his conscience if he funded it so that there was no taint on the wedding and you would then have no involvement.
JWs are happy to take from others but give nothing back they will expect gifts and goodwill from others but will give no compromise. Weddings should be a happy family event it is ridiculous that it becomes a staged advertorial for the organisation.
It is also concerning that the grooms family are behaving so badly and making a fuss about your daughter being involved in the wedding. It is none of their business who the bride picks.The wedding plans have changed so much that it now has nothing to do with the bride and groom at all.