Speaking from the pov of the one to do the humiliating, it depends on the situation.

If her brats are still young, and still sucking her tits almost as often as I do?
I'm cumming on her fat tits, specifically aiming to have her fat nipples dripping with my own milk. Even if she cleans them after, in her mind they'll never truly be clean. They'll always be stained by the feel, smell, and taste of my cum, and she'll always see her tits as my fuck jugs first and foremost, her family's milk producers a distant second, feeling perverse every time she uses them for their natural purpose. It will ruin the most important bonding experience that can exist between a mother and her son or daughter, and knowing I've broken that relationship before it even began, will turn me on enough to be ready to go again as soon I'm done smearing my cum all over her tits.

If her family are nearby? Like I drag her into the other room during a family Christmas or a school play?
I'm either cumming on her face, or cumming on her tits. Then I'm making sure she doesn't have time to clean herself up before she gets shoved out the door to face her family.
If it's on her face, then she's gonna struggle to wipe it off while anyone who notices, desperately tries to convince themselves they were wrong and at fault for even thinking that.
If I cum on her tits, I'm making sure it soaks through her top, and gonna laugh as her son and/or daughter goes in for a big mommy hug, and she has to choose between rejecting their hug, leaving them feeling unloved and unwanted, or accept their hug, rubbing her cum soaked tits all over them, and hoping they don't feel or smell it, and she doesn't leave them stained with my cum too.

Though the mom is the only one feeling humiliated there, not her son or daughter (untill I decide to tell them all about it 😂)

Also always wanted to make a mom jerk me off onto her kid's most treasured belonging. Their lucky t-shirt, the expensive telescope they worked their ass off all summer to save up for, a poem their first love gave them years ago, the trophy they're most proud of, the Teddy bear their grandmother gave them before she passed away. Then leave the cum there to eventually be discovered, leaving them wondering why the thing they value most in the world, is sticky, stained, and smells bad.

Is there anywhere a video where a mom insults her son during sex with her lover?Is there anywhere a video where a mother insults her son during sex with her lover?

Now imagine if your mom was on that show sucking on different guys cocks every night while she knows that you know. Was your mom hot when she was younger?

Did your mom understand that you meant that you wanted to see her on the show? I mean if she read between the lines its obvious but I am not sure she did.

https://thisvid.com/videos/betraying-her-family/

https://www.heavy-r.com/video/165647/Teen_Catches_Mom_Fucking_Her_BF/

Been absolutely years since I saw this, n Idk if this one really counts for this thread, but I thought it was hot. It's her daughter and her daughter's friend (or sister) not her son, and it's from the daughter's pov not her slut mom, so you don't actually see anything, but the milf isn't even trying to be subtle or hide what's going on. The girls have no choice but to listen to some random guy fucking the absolute shit out of their mom, hearing their mom moaning like a cheap slut, n making jokes to try n hide their embarrassment, but you can tell they're visualising it.

That's the thing for me. Even compared to other taboo fetishes, if we were to compare it to traditional mom/son incest, of course the idea of a mother and son copulating is extremely taboo. But there is a "logic" to it in that it's still based on the concept of the strong, natural mother/son bond, just perverted to the extreme. But the idea of a mother choosing carnal pleasure over her own son, now THAT is the most extreme taboo. Especially if the mother becomes completely corrupted and her humiliating her son becomes part of the kink.