"The old boys have wine and cookies."
Translation:Starzy chłopcy mają wino i ciasteczka.
Yeah, this is this super weird exception that is totally illogical, I'm afraid. "chłopaki" use the 'not masculine-personal plural' forms in Nominative. Meanwhile, "chłopcy" use the masculine-personal ones as they should. I guess you just have to remember that. Luckily, I believe this is the only such weird exception.
When I say 'in Nominative', I mean that in other cases it behaves logically, actually. For example in Accusative it's "Widzę chłopaków", as it should be, not "Widzę chłopaki".