I can think of a number of parents who could have written your post. Many are annoyed at the antics. But I also think of the parents of Steve Martin, Gilda Radner, Martin Short, Sarah Silverman, Robin Williams, Wanda Sykes, Amy Schumer and all of the Marx Brothers. How awful it would have been to stifle that comic genius!
I think you can try to celebrate it, but also have a code word/phrase that nicely says "Dial it down." Sort of like when we say "Inside voices, please" to kids. If yours knows that there is a time and a place for creativity and buffoonery, and a time for decorum (the classroom, church, a funeral,Thanksgiving dinner, or while you're on the phone), I say, let it go. If he's entertaining himself or your little one, and if he's not being cruel in making fun of someone, fine. Your little one can learn the same code words, and your older child can be the role model in showing him how/when to stop. Like playing "Freeze Tag," you know? Or when a parent says "STOP!" at the curb, and there is no going beyond that and into traffic.
If he can't control it, that's another story. But we have kids stuck on their electronic devices that they don't get up and exercise and do creative things, so I guess I'd be more enchanted than annoyed.