What an awful situation - my heart goes out to you.
I am sure that you have everything that he needs. Generally on their first day, they just need the rightcoour trousers, top and black shoes. I would ask his teacher at the end of school if there is anything else he needs in terms of pe kit etc, whcih he won't need on his first day.
No matter how good the school is - you will find nasty kids unfortunately. If you have any long term worries, I would speak to the head. I don't think they would calss one stupid comment from a child at this stage as bullying.
As much as this might be difficult for you, on Monday, you need to put a big smile on your face, be really positive and tell your son what a fantastic time he is going to have at school. Please don't let him hear any negative comments from you, as this will impact on your son and he wil take long er to settle.
My son didn't want to go to school (despite is being the best school in the area) as non of his friends were going. It was difficult for the first week and we had plenty of tears from him and holding onto me. I had to stay strong and svae my tears for when I was out of school. I got his teacher on side and she gently, but firmly took him into the class and I walked away. He is going into year 2 next week and loves school and has a huge set of really good friends.
Good luck for Monday. x