This is especially true 【among children from families and communities】 that have the resources （needed） to organize and sponsor sports programs and make sure that there is easy access to participation opportunities.括号里面是修饰语,小括号修饰resources.完整是the resources which is needed,中括号是表示人的范围.这句话的意思是：非常正确的是：在家庭和社区的孩子,拥有所需要的资源去组织和赞助体育项目,并且确保这里拥有简单的方式去获得参与机会.