But, a question must be asked: how does Shaggy earn a living for the three of them? The only way this guy could survive is if his rich uncle (Casey Kasem and Matthew Lilliard in dual voice mode) left him a fortune, otherwise they'd starve and be very poor!
Well, I'd imagine Shaggy in the culinary arts since he enjoys cooking, then Velma, I'm sure with her brain her job would bring in some dough! They would survive and their daughter would grow up normal!
I think that Shaggy enjoys eating more than cooking, and wouldn't even be able to concentrate on studying for said career (in the third live action Scooby-Doo movie, he's shown to have been held back for quite a while [showing that he's either slightly retarded or severely learning disabled!]) He would need some extra special help if he was going to be a chef or cook, as one or the other of these jobs is very intense study-wise (much like medicine or law.) Maybe his rich uncle can help him out on that one, or at least support him and Velma until he's able to succeed at what he wants.