My DS works at a restaurant with a tip jar (not Sbux). His nightly split of the jar pays for most of his weekly expenditures, and he's able to save his entire paycheck. He estimates it's about $2.00-2.50/hour additional pay per week, so he would be completely ticked and probably quit if the jar labeled "Tips" on the counter was dumped into the company till by the manager. I wouldn't blame him in the least.
Regarding "table/booth rent," it's not frugal to bring food/drinks to a business that is selling food/drinks. It's cheap. If you choose a place of business as a meeting place, then be willing to pay for the service rendered. Otherwise, go to a public (i.e. free) location as others have mentioned. As a parent, frugality is a good behavior to model for my kids, but I don't want to seem like I'm always looking for the free ride or how to take advantage of a person/business. Err on the people-friendly side of that fine line, and your kids will have a better role model. This is similar to drawing the line on honesty--e.g. extreme couponing that takes advantage of register/UPC loopholes, cashier mistakes "in your favor," free birthday voucher that you reuse if the cashier doesn't collect it from you. All of these save you money, but they cross a line that I don't want to model for my kids. If my kids watch me live by the "if nobody sees you, it's okay as long as it falls in your favor" creed, then they're almost certain to meet or surpass that line in their adulthood.