Hi, I'm really sorry that his visit to Québec City is for such sad circumstances. In terms of flight and Airbnb, the prices you found are very reasonable. For the car, in what area is his friend's family? If his Airbnb is close to Laval University, as are his friend's family, he may not need one. Taxis are plentiful, as are buses. It would be cheaper to get a 3-day bus pass for example, than rent a car. Even with the taxi/uber to and from the airport.
And for food, if he's in an Airbnb, he can get a few things from the grocery store for even less than 140 CAD.