However, it's not polite to take the call, then talk loudly at the table while your companion just sits there, feeling stupid. The proper etiquette is to excuse yourself and step outside to take the call, then return to the table as quickly as possible. Restaurants need to know ahead of time about any extra people or props you are planning to bring, especially if they are loud and overly intrusive to other diners. You've got to tell the restaurant you're doing that. They stop the whole show.
Restaurants routinely charge a certain fee per customer to cut the cake and serve it.
Once you factor that in, you might prefer to order the cake from the restaurant itself. In these high-tech times, restaurants have no problem taking two credit cards and charging two customers for their part of one check. Getting stiffed is not fair to a server who has worked hard to make your meal go smoothly. A standard tip is 15 to 20 percent, but Hirschberg believes that you should make it commensurate with the service. If you had to flag them down three times, and the soup was cold, give 15 percent, or less.