Day of the dead is a Mexican holiday that worships the dead
The relatives of the deceased.
They build an altar.
A couple of days before November 1st.
The Dead (Zombies) eats them during the night.
It just means the altar is dedicated to such person; everything located on the altar -- flowers, meals and other personal belongings -- are there for him/her.
nov 1 and 2
At most, one or two weeks after November 2nd.
If it's just a day babysitting job, you shouldn't need anything. If it's overnight, you'll need a change of clothes and toiletries.
To make a special offering to the altar also known those who past away
The music the deceased used to like. If the people you are mourning liked reggae, salsa, jazz or classic, you would be playing such kind of music before the altar for day of the dead.
Everything you will need to live day to day that is not provided at the cottage, i.e. food, clothing, eating utensils, cookware, money, maps, swimwear, towels, toiletries, etc.