When you return from giving the bag to Pigpen, give Linus the lemon sucker. He will give you his invitation to the party, and you can pick up his pen from the desk.
Finish trick-or-treating then visit linus in the pumpkin patch.
Linus is in the pumpkin patch to the right.
After Linus mails his letter, go left to where Lucy and Charlie Brown have the football.
Linus and Lucy live in the blue house. But you will find Linus in the Pumpkin Patch, to the right.
The pen, which you need to do the Charlie Brown football scene, is on Linus's desk in Linus and Lucy's house. It will appear when Linus is writing his letter to the Great Pumpkin. This is after you have selected the pumpkin in the pumpkin patch and rolled it back to the house. Take the bag that Linus gives you and give it to Pigpen on the sidewalk outside. He will give you a lemon sucker. When you take this back inside and give it to Linus, he gives you his invitation to the Halloween party, and the pen is on his desk. Linus is writing a letter to the Great Pumpkin.
It is on the table after you give Linus the lemon sucker from Pigpen. Linus gives you his invitation to the Halloween Party, and he has just written a letter to the Great Pumpkin. Pick up the pen.
you wait for the great pumpkin!
When you give him the lemon sucker from Pigpen. He gives you his invitation to the party, and you can get his pen from the desk.
It is under the pile of leaves.
It is all the way to the right, and and Linus is there.
He shows up when you first enter the island, getting his party invitation. But you will not see him again until you finish the process with Linus and the Pumpkin Patch. You have to choose a pumpkin for Lucy and roll it safely to her house. Then take Linus's bag and give it to Pigpen, and the lemon sucker back to Linus. Once you have his invitation, and the pen, you can go left into Charlie Brown's back yard where he and Snoopy are gathering leaves.
The pumpkin patch is both the first and last point on the island quest. You go there initially to see Linus, and return a pumpkin to Linus and Lucy's house. From there you swap Linus's bag for a lemon sucker, and swap that for an invitation to the party, before going left into Charlie Brown's backyard.