I am pretty sure he will be protected under the Family Medical Leave Act since he has been with the company for over a year. You need to look it up and double check, but basically it says it protects his job in the event of a family emergency, for up to 12 weeks. There is no guarantee of being paid, but you cant be fired. As far as not letting him take his vacation time- does the company have an HR dept? He needs to get in contact with them asap, because this is not allowed. If it is a small privately owned restaurant then you will have a harder time, but a regular corporation has rules in place about things like this. They can't give him a hard time. I totally get how demanding restaurants are, but I have never worked for one that would seriously try to pull something like this, and in the past when I had to go to a funeral, there was no question of whether I would go. My bosses just told me to get going and they would take care of it.
I'm not going to say to quit his job though. Never leave a job without a new one in place, especially in this economy. Jobs are too important and hard to come by. But just check out FMLA and talk to HR, because they really can't do this. They would be opening themselves up to a lawsuit if they tried to prevent him from going.