Can I interplant various pumpkins and squash, or will they somehow interbreed? I'd like to do some sugar pumpkins, mini pumpkins, and a gourd assortment. Do I need to keep them separated? If so, by how far?

Probably by about a neighbor or two...yup squash definitely will do that, but usually separation is needed if you save seeds, I hear folks swear they won't cross while growing, but I am here to tell you that summer squash was changed to a zucchini by the end of the vines life. Calabasa is also an easy cross, they are all just so much alike

Depends on the species. They will not cross across species, but readily cross within species. Most summer squash except Trombocino are C. pepo. Many pumpkins are also C. pepo, but some C. maxima. C. moschata, and C. mixta are also sold as pumpkins. Winter squash may also be C. pepo, C moschata or C. maxima. Within species, they are insect pollinated, so to save seed they need to be separated further than a bees flight path. Not a problem unless you are saving seeds as the cross does not show up until the second generation. I interplant, crooknecks, straightnecks, scallops, zucchinis acorns, delicatas which cross promiscuously. But not in the immediate generation. Saved seeds or volunteers will result in some weird squash tho.

@FarmerDill.🙃thanx