Isn't it ironic that the very people who are most ignorant of guns and hunting are the ones who most want to do away with both?
In that situation, I would just try to find a relaxed atmosphere to sit down and talk one-on-one with both your daughter and her husband. I would not try to push my beliefs or ideals on them, but I would try to express what my hopes and desires for my grandchild were (@learning to shoot/hunt/love the outdoors). Then I would ask them about what their goals and desires are for their son as well regarding the shooting/hunting sports. I would ask them specifically to explain their reservations, concerns, what they see as risks, and really listen to their points of view.
Then I would try to create some kind of beginning activity that would meet their goals and introduce your grandson to shooting/hunting in some way. Then I would propose it to your daughter and son-in-law in a way that they can see you are trying very hard to satisfy their reservations and concerns (respect their judgment). Hopefully they will see that you are: 1) very serious about introducing your grandson to shooting/hunting sports, 2) geniunely concerned about their reservations and goals, and 3) willing to put some thought and effort into satisfying their concerns. In my experience in dealing with all different kinds of people, most of them are willing to compromise in some way if you show that you both believe in what you are proposing (but not to the exclusion of all other points of view) and are willing to work to find some common ground that respects their chief concerns.
Good luck with your efforts. :wink: