I placed all my corrections between two (), comment if something is not clear.
Is (to) set a date and find the location.
out the menu, (as well as the) entertainment.
input from other(s) and (assign) them tasks to (complete).
mail the invites out(no s).
or event (got underway, I would)
the guests(s) (were) having a good time.
Explanation:
Everything happened so suddenly that it is maybe too hard for him to accept all these things one after another and be responsible of his own life this quick. Losing parents is a nightmare of every child and he is going through the same situation that no one will ever wish for. Of course changes can be seen and it's absolutely normal. He can do what he likes and calm down his mind to finally cope up with the situations slowly. Moving on takes time and time heals everyone. Brian will come to peace with his emotions and his grades will gradually improve. All he is need for now is peace of mind to relax.. His cousin can help him by giving him company, by being his friend, by listening his sorrows..that could be a great help. Genre would probably be drama I guess