If that doesn't work or if it seems like too much effort for potentially too little in return, I suggest a very brief conversation-one that lasts little more than the time it takes to rip off a Band-Aid. "Can we have a conversation about dating apps?" is one way you might start it. It gives him agency in case he has similar concerns about dying of embarrassment.
Blocking need not be a coordinated endeavor. You could make your profiles anonymous-ish by keeping them face-pic-free for a while in the hopes that you will come across your son's profiles and block him before he ever gets to see you.
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