At the Halloween party, completing all 4 games should prompt Charlie Brown to say that you are going trick-or-treating. There is a glitch where this does not happen and you are left alone (you have to restart).
the answer is NO.
When you finish the 4 games (including the pumpkin drawing), Charlie Brown will announce that you are going trick-or-treating.
Once you finish trick-or-treating, take the candy to the pumpkin patch and give it to Sally.
you grab the mask on the scarecrow and go into the house
There is no pigeon on great pumpkin island.
The pumpkin patch is to the right on Great Pumpkin Island. It was the only area shown in the island preview.
you find him eatin candy
There are no buildings or upper rooms on Great Pumpkin Island.
The pumpkin head is one of the 4 games at the party, which occurs after Snoppy's adventure. The "pumpkin head" costume is not on Great Pumpkin Island. It is a costume change that can be triggered (and reversed!) by typing the costumizer command : Ctrl +Shift +P (all at once). This does not work as a costume on the island. You have to find the mask on the scarecrow and wear it.
The name of the island is Great Pumpkin Island. See the related question below.
you wait for the great pumpkin!
At the very end, there is a mysterious figure in the pumpkin patch!