I don't think that you have to immunize your children. You need to look into your public health laws and into exemption forms. You are probably able to have an exemtion based on religious or concious belief. I suggest you fill out the forms so your children are legally exempt or if they don't require forms have a letter drawn up legally stating your choice not to vaccinate and have it notarized or certified by a public health official.
As I'm not totally clear on the state law, maybe search around the following site or contact them for more information.