H.S.
If his grandparents are enabling the problem with your son wanting the bottle, then you can do one of two things: either one, tell them straight out why he isn't to get a bottle any more and if that doesn't work, don't take a bottle with you. My grandmother watches my two kids and she used to give him bottles of milk when she would put him to bed (I take evening classes) which a family friend who is a dentist said was bad for his teeth. Point out that giving children a bottle after they have teeth is bad for the teeth and they can even cause decay when they are older. Don't give in when he cries, that's something all kids do when they don't get their way (as I'm sure you know from experience.) Good luck and don't give up.