people are enjoying food at a crowded restaurant.
The people are celebrating their father's birthday at a local restaurant.
People enjoying food at a restaurant does not mean they are celebrating a birthday or anything for that matter.  Just because the restaurant is crowded does not mean that it local to the people.
There is no indication there is a father's birthday celebration, or that the restaurant is local, or that the people even know each other.
The people could have been out of town instead of eating at a local restaurant. The people may not even know each other, let alone celebrating their father's birthday.