They just know that they're doing it without them. I happen to like my work. And I try to convey that to our daughters. That's why I do it so much. Kids understand that way of thinking.
Free agents have to do everything.
One solution is to enlist your kids. Toss them in the car when you have to race over to Kinko's or drop a package at Fed Ex. Ask them to stamp envelopes. Bigger kids may even be able to proofread copy or fix your computer. So make your microbusiness a family business.