You are fortunate to have both sets of grandparents near you, as children need to know and spend time with them. Likewise, contact with the grandchildren—and with you—means a great deal to the grandparents. But, let’s face it: grandmothers are just mothers-in-law in disguise! Can you think of any type of joke more common than the mother-in-law joke? They’re unkind, but we usually laugh. And, in your case, you’ve got a double dose (both mother-in-law and mother, and, presumably, father-in-law and father).
I think I’d play this scene rather lightly. Whenever one visits and offers a play item that looks iffy to you, say something like, “Wait a minute, Mom, and let me have a look at that. You know I’m a nut about toy safety. I probably over-do it, but it makes me feel more secure.”
If you don’t think it is safe, don’t reject it altogether. Suggest, “Do you mind if I put this back until he’s a little bit older?” With this kind of acceptance of their good will, I think they’ll be less resentful of your control and instead will be impressed with what a good mother you are. And it certainly sounds as though you are one indeed. Keep it up.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.