More People At Once
If service or production is slow simply tap on decorate then Waite about 5-10 seconds then hit exit. Then people will start crowding in like crazy repeat as you wish.
Serve More Food
It is possible to serve food from the stove to the serving plates provided the food cooked is the same as the serving dish you are placing it on. There is no need to wait until the serving plate has been cleaned before adding more food to it.