I think it partially depends on the type of restaurant you're working.
1) Is it an atmosphere where people will want to have closer to 5 or closer to 10 minutes taken up by you?
2) Why not use both? You can alter it as time/audience dictates. If your first goes well and they respond favorably you know you can go for 3 rather than 2.
3) How fast does the place you're working get food to the table? Obviously if they're turning in orders and getting them to the table too quickly you're going to want to go for a shorter routine.
1) In between
2)I will try
By the way I have never actually did magic at a restaurant. (The manager, my family knows very well, says she wants me to sometime. I don't know when so I am going to try to get a heads up so I can actually learn instead of like some people that just do it without knowing. It is a local restaurant.) I did not want to make another topic so I used this topic.