The best thing you can do here is get over 200 pieces of candy, but even that's really hard, so here's what you gotta do. There are probably more ways to get this much, but I'm 100% sure this methodworks. Most pieces I got was around 226.
Go down and right and pick yourself a pumpkin (size doesn't matter). Before you go back to your mom now, go to the costume shop and march down from the door in a straight line. Then head back as soon as your mother gives you the signal.
Take the green man costume first, and go down to the church (south-west) as fast as you can, ignoring all the other houses. Trick-or-treat there and you've got a whopping 80 pieces to start with. Head back to the shop again and change into the knight costume. Trick or treat at all the houses (except the one right of the costume shop) in a clock-wise motion for another good 90 pieces and head back to the shop again. Now take the bonka and do the south and west side of the shop, this should give you well over 200 pieces with seconds to spare.