Well, in 5 years he will have either heard it from you or heard it from his friends.
Also, holy shit, this is tough one. Sex work is legitimate work, but his friends, primarily young men, are not going to be cool about this; especially if there are lap dances involved. On the other hand, it keeps food in the pantry and heat in house.
If it were me, then I would rather here it from my mom than from my friends. In addition to maintaining an honest relationship with your son, this also protects you. Men are pretty fucked up and it is not a stretch to imagine that your sons’ friends or their fathers could use the threat of telling your son about your night work as the basis for sexual exploitation. At the very least, it would draw some dads’ attention your way that would cause nothing but problems. Consider explaining how much of your income is derived from stripping and then explain what it pays for. Be ready for him to suggest alternative occupations with knowledge about what your finances would look like if you switched. This will help him understand the why behind your work and allow him to arm up on return-fire jokes.
These types of jokes would, of course, be crass, and aimed at either the unfuckability of other kids’ moms or at their dads’ priorities; for example, their dad is willing to pay for his college but not their own sons’?
Additionally, this whole conversation may be a net positive for his personal views on porn, having a humanizing effect on the woman that he would otherwise see as objects. Life is hard and people do what they can. It’s a weird facet of our culture that sex work is so readily consumed AND so readily looked down on.
Finally, and this is speculative at best, with the GOP pushing a federal anti-porn bill through the house and senate, strip clubs may see an increase in foot traffic, thereby increasing both your income and your likelihood of your son finding out. It may, also, make this line of work illegal and therefore more dangerous.
All of this is for consideration and, unfortunately, none of this answers your question directly. Truly, this is an ethical question for the ages.