Would you turn someone in if you could not remain anonymous?

After my 94 year-old grandfather mentioned to me that he had driven over 150 miles last Friday, I decided it might be time to take the bull by the horns. He is not a safe driver. Period. As I’ve mentioned here before, his children refuse to take his license and my father even told me that if they took it, it would be as good as killing him. So I did some research and found out that I can fill out a form with the DMV to have him brought in for a driver’s test. The only problem is that I can’t do it anonymously, I have to list my name and address along with why I think he should be tested. My family would certainly find out who set this in motion and there would be hell to pay for my not minding my own business and letting his children deal with it. Would you complete the form?