I have two boys and a younger girl. My DD wanted boy bits to grow for her 4th birthday.
She is a different child, as is my eldest who's diagnosed Autistic. DD is intelligent in an academic sense (socially she has issues, we're all a sum of all our parts). She's nearly five and barely understands gender let alone different identification possibilities of gender.
4 year olds are wonderfully tolerant of difference because as little sponges they just except things. I don't think other children will give you any more bother than any other child gets.
With DD's differences (social issues, extreme anxiety, investigations for ASD) i approached the school and spoke with the senco. She in turn spoke to the class teacher and we hatched an action plan of how we would work together to ensure DD settled well.
You know your child best and you're best situated to relay your childs needs to the school. I find writing down key points helps keep me on track and focused when meeting with the school.
At all the schools my DC's have been too (many) we've been asked what name they like to be called/ we'd like to be used plus for forms etc their full formal birth name so from a practical point of view its likely your child can be reffered to as something they are comfortable with.
Many schools have a fairly gender neutral school uniform option i.e. Trousers, polo shirt and sweatshirt. If this could be an option for you then you leave your child the flexibility to develop and identify as they wish. Long hair will need to be tied back (regardless of gender), jewellery etc isn't allowed any way.
Having a child, or two, who don't quite conform to societies norms has its challenges and one of those is the reaction of others. For years I felt very criticised by others. That is not a reason not to have pursued what I felt was best for my child(ren).
Good luck in your journey.