Line a baking pan with some loosely crumpled (perhaps reused) aluminum foil. Purpose is to prevent the upright halves from overturning and spilling the contents. Maybe you can find a way to wedge the halves tightly against each other, to dispense with the foil.
Fill each squash half with equal measures of sweetening and butter. Brown sugar or maple syrup are the best sweetners for squash. If you're cutting calories, a teaspoon of each will do. If you want to tempt the children with a veggie that's almost dessert-like, you can fill the cavities. Spinkle with salt and plenty of black pepper. Top each with a handfull of pecans or walnuts.
Roast the filled squash in a medium oven for at least an hour, possibly as long as two hours. They'll be done when the flesh has darkened from the sugar carmelizing and a skin has formed on the top rim. If the small ones seem to get done ahead of the large ones, add some water to their cavities to prevent them from drying.
Take the roast squash halves out of the oven at least 15 minutes before serving time. Let them cool a bit and then, using a serving spoon, lift them out into individual serving bowls.