I think the issue here is not the actual issue here if that makes any sense at all...I don't think the issue is actuall ythe bank account

I can understand your opinion and I am not sure how I would feel about this topic but I do know that both my mum and PIL would respect the wishes of dh and i with regards to our kids.

As dd's mum you have your right to an opinion and a vote and as dd's dad your dp has a rght to an opinion and a vote, seeing as you don't agree with each other someone is going to have to compromise..or both will have to compromise, but that is something that has to be decided between you and him as a couple and co parents. Nothing to do with the grandparents and their opinions.

If it's a bank account today what is it tomorrow, religious decisions, education decisions, where to live decisions etc etc Grandparents are wonderful things they have a very special role that others not even mums and dads can fill and they can give advice on pareneting and marriage etc etc but only when both partners want this. I think it is very important for you and dp to develop as parents together and to make the decisions, others can advise but not get a vote, it can take a while to develop in these new roles, flip it seems to me for the rest of your livers you will be developing and growing as parents.

I think your dp is being unreasonable in his ultimate in fact that is beyond ridiculous but maybe it would help to sit down and discuss each others opinions and go from there?