I never wear sweatpants anywhere except in the house. If I go out into the real world I'm carrying tools.......
Oh and I'm assuming I can only drink beer or whiskey correct? Anything else and I'm not a man I assume?
If you're just lounging around, I'd maybe look into a smartcarry holster or something similar. If you're actually looking to get sweaty, hmmm.. shoulder holster? it'd be pretty common to see sweatpants and a zip-up sweatshirt or vest around here on the weekends, and either could conceal easily.
When it's not minors wearing them, I prefer them to be long enough to cover everything, but short enough to keep things interesting. This was the same approach I took when writing papers in college (I call it the Skirt philosophy).School girls skirt length should be long enough to cover the knee. There's no need for that kind of immodest apparel among minors.
I think a fanny pack holster would be a good option. I'm mean, it's not like you're concerned with looking like a dork if you've already got sweat pants on.
Sweatpants...for those who've given up on life.