You could try calling in a wildlife charity to carry out an environmental assessment of the area (RSPB? etc). The bio-diversity can probably be greatly improved by spending a modest amount on plants, bat boxes, etc. Also the way that the grass areas are managed can also have a big beneficial effect. Doing this as part of the development can greatly improve the ecology that is currently there and will address point 2 in their objections.
PS. Make sure you don't have Great Crested Newts in the area!