what if my grandparents shunn me and hate me
They well might, but if you are genuinely being led by the Spirit you will not regret making your calling and election sure (2 Peter 1:10)
Mat 10:32-39
(32) Whosoever therefore shall confess me before men, him will I confess also before my Father which is in heaven.
(33) But whosoever shall deny me before men, him will I also deny before my Father which is in heaven.
(34) Think not that I am come to send peace on earth: I came not to send peace, but a sword.
(35) For I am come to set a man at variance against his father, and the daughter against her mother, and the daughter in law against her mother in law.
(36) And a man's foes shall be they of his own household.
(37) He that loves father or mother more than me is not worthy of me: and he that loves son or daughter more than me is not worthy of me.
(38) And he that takes not his cross, and followes after me, is not worthy of me.
(39) He that finds his life shall lose it: and he that loses his life for my sake shall find it.