That's a great idea. Squash and pumpkins are ideal for growing with little kids since the big seeds are easy to handle and sprout quickly when planted into warm ground.

There are two meanings to "hills" when used in gardening. Sometimes it just means planting in small groups spaced a distance apart, other times it means actually forming a small mound and planting a group of seeds on top of it. The latter is commonly done to improve drainage and to help the soil warm sooner in the spring -- sort of a miniature raised bed.

If your local farm is using elevated hills to plant their pumpkins its probably desirable for you to do so, especially if you're on clay soil.

To make a squash/pumpkin hill I like to dig about a pit about 8-12 inches deep and 12-18" wide -- size depending on how large and vigorous the chosen variety is. I fill that pit with compost and, if conditions are dry, water it well.

Then I mix more compost and any necessary soil amendments -- lime, fertilizer, ??? -- with the dirt I dug out and pile that back on top of the compost-filled pit. I form that into a slightly dished, flat-topped mound 8-12" across and, if conditions are dry, make a small moat a few inches from the base of the mound.

I plant 4-6 squash/pumpkin seeds, again depending on how large a variety it is, in a circle on top of the mound.

Once they come up I have to steel myself to thin them to two plants of a large variety or 3 plants of a small one. I know I have to -- otherwise all the plants will struggle when they're older -- but I truly hate it. LOL

As for the grass, you'll want to clear a few feet around the hill so that the grass won't compete with the pumpkins for nutrients and water, but I've always planted my long-vined varieties at the edge of the garden and let the vines run out onto the lawn. That can get a little messy because you can't mow or trim close to the vines, but my DH isn't too obsessed with the look of the lawn so we're OK with it.

You can line your hills up in rows or arrange them in a grid, both ways work.

I don't think there are any borer-resistant pumpkin varieties. Most of what we call pumpkins are C. pepo or C. maxima and both those species have the hollow stems borers love. C. Moschata squash are borer resistant because of their solid stems and there are some round varieties such as Long Island Cheese and Fairytale are readily available. Unfortunately for gardening with a child, these don't have the upright shape and bright orange coloring of the traditional jack-o-lantern pumpkin.

If you read through back postings you'll find a lot of information about defeating the SVBs. When I lived in PA and MA I never had any significant borer issues but I always took the precaution of throwing a shovelful of compost over the leaf nodes every yard or so in order to encourage secondary roots just in case.

Since you've grown pumpkins before I'm sure it will come back to you once you get your hands into the dirt. Good luck and I hope your little garden helper enjoys it as much as my little helpers do.

While there are pumpkin shaped C.moschatas,Autumn Buckskin, Rumbo, Cow, Dickenson etc, they are not orange but buff in color.

Here is a link that might be useful: Autumn Buckskin