With a little guidance and a couple of days, they will do the job for you.
1/8" or larger drill bit
smooth peanut butter
Step 1: Drill guide holes
Start with an uncut pumpkin. You do not need to open it up and scoop out the guts. The squirrels do that for you.
Using a drill on low speed to reduce spattering, start out by drilling holes where you want the final holes in the pumpkin to appear. As shown in the first picture, I have drilled 1 hole each for the eyes, nose and a line of holes for the mouth. Drill all the way through the pumpkin flesh.
Drill around these holes to make the openings bigger as shown in the 2nd and 3rd photos.