My youngest son is getting married next month. Would it be wrong not to bring his elderly grandparents to the wedding?

Maybe you could show them a video of the wedding.

The fact that you’re asking here tells me that we think very much alike. I think given the same situation that I would ask the kids first, then ask their grandparents. They may surprise you. If they should say they’d like to come, let them know that arrangements will need to be made for someone else to bring them to/from and tend to their needs before, during and after the event. Be sure to talk to the kids about Grandparents clothing, meds, toileting, accessibility, and no place to rest. Should they still decide yes, can you hire a close friend or someone from the facility?
My Grandparents came to my sons wedding ceremony and only stayed at the reception long enough to be announced as a special guest.
No matter what you decide it’ll be a great day because you are planning ahead. Congratulations!
Here is a geriatric doctors advice:
https://www.ctpost.com/news/amp/Confusion-reigns-as-to-whether-elderly-mom-should-2028807.php