The ultimate Halloween can be achieved with little money. Don't worry about not having 'fabulous' stuff. I often think I had a funner Halloween when it was more about fun and less about acquiring stuff!
We always made our costumes out of old clothes, cheap fabric, and Mom's makeup. Old hats, funny shoes, etc.
You could stuff some plastic grocery bags with leaves and then use the bags to stuff a set of old clothes to make a scarecrow. I made a scarecrow that way, and used an old pair of shoes stuffed with newspaper to give him feet. If you don't have tools or supplies to put the scarecrow in the ground, let him sit in a chair in the front of your home. You can put an old hat on him. Get some trees out of the woods and prop the trees around him....gather some rocks and do the same thing. A bag of fake spider webs goes a LONG way!
One year I got old metal cans and washed them out, and filled them with water. Freeze the cans until they are rock solid ice, and then get a nail and a hammer. Draw a pattern of any kind and use the nail to carefully punch holes in the can. When you are finished, you will have a free luminary/lantern if you have some candles to put in them! If you can get a can of spray paint at Walmart very cheaply, and paint the outside black, brown, white, etc. Be warned, the nail and hammer part will take awhile, and the kids should probably just draw the design and an adult do the labor. Simple designs are best.
Also, the icky Witch's Kitchen or Mad Scientist's Lab: Bowls of frozen, peeled grapes, shelled hardboiled eggs, cold cooked spaghetti, perhaps mini whole pickles...you can use anything!
Tell the kids that a witch or scientist left some specimens/experiments in the kitchen, and blindfold all of the kids. lead them in to a darkened kitchen, with spooky music playing. One by one, lead them to each dish of cold and creepy food, and make up an icky name for each dish ahead of time/ As you slowly plunge their hands in each dish, make sure you tell them what they are supposedly touching- intestines...worms...baby alligator tails....anything you can think up. When they all have felt the icky, take their blindfolds off and have a good laugh.
Don't forget apple bobbing. Walmart has seasonal plastic tubs for less than 5 bucks- or find a container around the house. A few apples, and you are in business!
Have a great Halloween!