I think poison is less humane than the trapping method for the removal of Indian Mynahs especially if the trapped birds are euthanised by a vet or the like. Providing seed (not recommended) is going to attract many different birds and ensuring only the target species eat the poison is going to be very difficult so you may kill the remaining wanted native birds in error. May I also suggest that you plant some spiky native plants and grasses rather than only nectar providing plants as these will provide habitat and safe havens for other birds who are intimidated by the IMs and will help discourage the IMs as well. Diligent removal of nesting material and eggs from IM Nests will also help but these measures need to be followed by your neighbours too as the IMs and the native Noisy Miners can be invaders of neighbourhoods rather than individual homes. Good luck it is possible to achieve.