A: No. A parent is responsible for child support until the age of maturity -- 21 yr old. In some cases this can be extended until post college, but usually requires several variables. Also, In NY under very limited circumstances can a handicapped child receive child support past age 21.
A: The law says that parents have a 'fundamental right to raise their children as they desire', including who visits their children. Therefore, in New York the court will only grant visitation to grandparents if doing so would be in the best interest of the child.In New York, grandparents have a limited right to visit their grandchildren. Try to resolve with your son it may be faster and easier. If that doesn't work you will need to file in family court for visitation rights.
this may offer you some hope: http://www.nysun.com/new-york/ruling-favors-grandparents-seeking-visitation/48830/