Creating a riverside wildflower meadow

My question is: I would like to create a wildflower meadow in the 4-acre riverside sheltered field that adjoins my cottage. I need to remove tough grass but preserve certain areas which are filled with bluebells in the Spring. I have researched the basic principles of creating such a wildflower meadow but would like to know a bit more about what are the best means and machines for taking up the dense grass in such a large area- and keeping it under control without resorting to hugely environmentally and health-damaging glyphosate.